JOHX  LOUDON  MACADAM 

The  Road-Maker 
Sept.  21,  1756— Nov.  26,  1836 


T 


THE  ART   OF 

ROADMAKING 


TREATING  OF  THE  VARIOUS  PROBLEMS  AND  OPERATIONS  IN 
THE  CONSTRUCTION  AND  MAINTENANCE  OF 

ROADS,  STREETS,  AND  PAVEMENTS 

WRITTEN     IN    NON-TECHNICAL    LANGUAGE,    SUITABLE    FOR    THE 

GENERAL   READER;     WITH   AN    EXTENSIVE    BIBLIOGRAPHY 

AND    A  DESCRIPTIVE    LIST    OF    RELIABLE    CURRENT 

BOOKS  AND  PAMPHLETS  ON  THESE  SUBJECTS 


BY 

HARWOOD   FROST,   B.A.Sc. 

Member  American  Society  of  Mechanical  Engineers 
Member  Society  for  the  Promotion  of  Engineering  Education 


NEW  YORK 
THE    ENGINEERING   NEWS   PUBLISHING    CO. 

LONDON  :  CONSTABLE  &  COMPANY,  LTD. 
1910 


QEHEKM. 


Copyright,  1910 

BY 
HARWOOD    FROST 


Entered  at  Stationers'  Hall,  London,  E.G.,  1910 


THE  SCIENTIFIC   PRESS 

ROBERT   ORUMMONO    AND    COMPA 

BROOKLYN,    N.    Y. 


TO 

EVELYN  LYNAS  FROST 

WHOSE      ENCOURAGEMENT     LED     TO     THE    PREPARATION 

OF   THIS    MATERIAL,   AND    TO  WHOM   I    AM   GREATLY 

INDEBTED  FOR  ASSISTANCE  IN  ITS  COMPILATION 

THIS  BOOK  IS  AFFECTIONATELY  DEDICATED 


PREFACE 

ROADMAKING  is  an  art,  based  on  a  science.  Although  it 
forms  one  of  the  most  common  and  most  important  engineer- 
ing works  that  engage  the  attention  of  man,  the  use  of  roads 
is  so  much  a  part  of  our  daily  life  that  we  almost  cease  to 
consider  their  construction  and  upkeep  as  problems  in  en- 
gineering. Yet  ROADS  may  be  said  to  be  the  backbone  of  the 
national  life  of  a  country  and  the  mpst  important  element  in 
the  progress  of  civilization  from  the  very  earliest  times. 

This  book  is  intended  to  give  an  outline  of  the  history  of 
road  building;  of  the  problems  that  confront  the  engineer  in 
the  location,  construction  and  maintenance  of  roads;  of  the 
properties  of  the  various  road-making  materials,  and  of  many 
other  features  of  the  subject,  and  an  effort  has  been  made  to 
present  this  information  in  a  style  suitable  for  the  intelligent 
reader  with  or  without  previous  technical  experience. 

No  claim  is  made  for  originality  in  the  contents,  or  for 
the  presentation  of  new  ideas  or  methods;  in  fact,  since 
the  days  of  Telford  and  Macadam  little  advance  was 
made  in  the  science  of  roadmaking,  until  the  comparatively 
recent  inventions  of  the  modern  mechanical  methods  of 
quarrying,  stone  crushing,  grading,  etc.,  and  the  various 
improved  methods  of  dust  prevention,  street  cleaning,  and 
road  maintenance.  In  the  compilation  of  the  material  the 
columns  of  " Engineering  News"  and  other  technical  period- 
icals have  been  drawn  upon,  government  reports  and  a  few 
trade  publications  devoted  to  the  making  of  roads  have  been 
freely  quoted,  and  a  large  number  of  treatises  have  been 
referred  to.  Foremost  among  these  may  be  mentioned 
Byrne's  " Highway  Construction,"  Baker's  "Roads  and  Pave- 
ments," Tillson's  "  Pavements  and  Paving  Materials,"  Aitkin's 
"Road  Making  and  Maintenance,"  Judson's  "City  Roads  and 
Pavements,"  and  "Road  Preservation  and  Dust  Preven- 

vi 


PREFACE  vii 

tion,"  Soper's  "Modern  Methods  of  Street  Cleaning,"  Spald- 
ing's  " Roads  and  Pavements/'  and  Coane's  "Australasian 
Roads/' 

The  majority  of  these  publications  so  specialize  in  one  or 
more  features  of  the  subject,  or  cover  the  entire  subject  in 
such  encyclopedic  detail,  that  they  do  not  appeal  to  the 
average  non-technical  general  reader.  On  the  other  hand, 
in  spite  of  the  modern  specialization  of  the  engineering  pro- 
fession, even  the  most  specialized  engineer  is  often  called  on 
to  make  use  of  information  regarding  some  form  of  road  work, 
and  although  he  may  be  a  specialist,  and  well  informed  on  the 
subject  of  drainage,  or  of  automobiles,  he  may  be  decidedly 
ignorant  of  the  methods  of  roadbuilding  and  maintenance, 
which  are  outside  of,  but  closely  allied  to,  his  specialty. 

The  present  book  has  been  written  for  both  of  these  men. 
The  object  has  been  to  condense  into  the  comparatively  small 
space  of  a  single  volume,  the  fundamental  and  essential  prin- 
ciples of  the  roadmaker's  art  as  presented  by  the  most  re- 
liable authorities.  It  gives  to  the  reader  unacquainted  with 
the  subject  a  good  general  knowledge,  and  to  the  technical 
man,  an  outline  of  the  main  facts  and  an  indication  where 
further  reliable  and  specialized  information  can  be  obtained. 

To  do  this,  all  involved  mathematical  tables  and  formulas, 
records  of  tests  and  analyses,  tables  of  statistics  and  the 
higher  technical  features  of  the  subject  have  been  omitted; 
information  that  covers  pages  in  some  treatises  has  been 
reduced  to  conclusions  and  tabulated,  and  such  illustrations 
have  been  selected  that  will  emphasize  the  popular  features 
of  the  subject. 

H.  F. 

220  BROADWAY,  NEW  YORK, 
March,  1910 


CONTENTS 

PAGE 

PREFACE vi 

POEM— " THE   ROAD."— ANONYMOUS xiv 

INTRODUCTION:     HISTORICAL     SKETCH     OF     ROAD     DE- 
VELOPMENT.. 1 


PART   I 

PRELIMINARY   CONSIDERATIONS 
CHAPTER   I.     RESISTANCES   TO   TRACTION 

Object  of  a  road — Causes  of  tractive  resistance — Power  required 
to  move  vehicles — Recent  experiments  in  tractive  resistance 
— Calculation  of  tractive  force — Rolling  friction — Effect  of  size 
of  wheels — Effect  of  springs — General  results  of  experiments 
in  tractive  resistance — Gradient — Loss  of  power  on  inclinations 
—Necessity  of  easy  gradients — Hauling  power  of  horses — Power 
of  teams — Calculation  of  load  on  gradient — Load  drawn  by 
horses  on  grades — Steep  grades  objectionable — Methods  of 
expressing  grade 10 

CHAPTER  II.  ROAD  AND  PAVEMENT  ECONOMICS 

Value  of  good  roads — Advantages  of  paved  city  streets — Eco- 
nomic value  of  road  improvements — Ultimate  economy  of  road 
improvements — Questions  affecting  design  of  city  pavements 
— Methods  of  payment  for  city  pavements — Administration  of 
highways — European  systems  of  management — American  sys- 
tems— The  labor-tax — Maintenance  of  city  pavements — Opening 
of  pavements 19 

CHAPTER    III.    PRINCIPLES     UNDERLYING    THE   SELECTION 
OF    PAVEMENTS   FOR   DIFFERENT   PURPOSES 

Road  and  pavement  definitions — Requirements  of  a  good  pave- 
ment— Properties  of  an  ideal  pavement — Relative  values  of 
qualities  of  different  pavements — Use  of  tables  in  selection  of 
pavements — Adaptability — Desirability  —  Serviceability  —  Com- 
parative safety  of  pavements — Durability — Cost 28 

viii 


CONTENTS  ix 

PART   II 

COUNTRY  AND  SUBURBAN  ROADS 
-CHAPTER   IV.     LOCATION   OF.  .COUNTRY   ROADS 

PAGE 

Length  of  straight  and  curved  roads — Comparative  advantages  of 
straight  and  curved  roads — Economy  the  basis  of  location — 
Value  of  scientific  road  location — Methods  employed  in  location 
— Characteristics  of  country  noted — Instruments  used — Contour 
lines — Topographical  map — Levels  and  bench  marks — Value  of 
saving  distance — Grades — Methods  of  overcoming  grades — Deter- 
mination of  maximum  grade — Most  suitable  maximum  grades — 
Most  advantageous  grade — Establishment  of  maximum  grade — 
Establishing  the  final  grade — Curves — Curves  on  an  ascent — 
Width  of  roadway — Selection  of  bridge  sites — Principles  to  be 
observed  in  final  selection — Method  of  final  location 37 

CHAPTER   V.     CONSTRUCTION   AND    PROTECTIVE    WORKS 

Earthwork:  Classification  of  earthwork — Equalizing  earthwork — 
Transverse  balancing — Natural  slope  of  embankments — Shrink- 
age of  earthwork — Making  embankments — Cost  of  earthwork  .  .  53 

Foundations  and  Drainage:  The  importance  of  drainage — Systems 
of  drainage — Object  of  side  ditches — Surface  drainage — Trans- 
verse contour 62 

Highway  Bridges:  Location — Classification — Bridge  trusses — Types 
of  trusses  and  bridges — Short-span  bridges — Low-truss  bridges 
High-truss  bridges — Plate-girder  bridges — Use  of  timber  in 
bridges — Masonry  and  concrete  bridges — Culverts — Size  of  open- 
ing— Floorbeams  and  floors — Substructures — Abutments — Most 
economic  bridge 69 

Retaining  Walls:  Where  retaining  walls  are  built — Drainage — Sea 

walls 87 

CHAPTER    VI.    MATERIALS    USED    IN    ROAD    CONSTRUCTION 

Most  suitable  material — Selection  of  material — Agencies  causing 
destruction  of  roads — Physical  agencies — Mechanical  agencies 
— Chemical  agencies — Organic  agencies — Essential  qualities 
of  roadmaking  stone  —  Hardness  —  Toughness  —  Durability — 
Cementing  value — Classification  of  rocks — Igneous  rocks — Sedi- 
mentary rocks — Metamorphic  rocks — Primary  mineral  constit- 
uents— Physical  properties  of  rocks — Conclusions  regarding  pav- 
ing stones — Principal  varieties  of  roadmaking  rocks — Granite — 
Basalt — Sandstone — Limestones — Sand  and  clay — Gravel — Free 
government  tests 91 


X  CONTENTS 

CHAPTER  VII.  EARTH,  GRAVEL,  SAND,  AND  CLAY  ROADS 

PAGE 

Earth  Roads:  The  first  step  in  construction — Preparation  of  road- 
bed— Preparation  of  road  surface — Drainage — Culverts — Main- 
tenance and  repair 117 

Gravel  Roads:  Gravel — First  course — Second  course 123 

Sandy  Roads:  126 

Clay  Roads:  126 

Sand-clay  Roads:    Essentials  to  success — Causes  of  failure — Cost  of 

sand-clay  construction 127 

Burnt-clay  Roads:    Fuel — Preparation  of  the  roadbed — Firing — Cost 

of  burnt-clay  constrution 133 

Tools  Used  in  Construction  of  Country  Roads:  Tools  for  clearing 
and  grubbing — Tools  for  grading — Scrapers — Road  graders — 
Elevating  grader — Carts — Dump-cars — Dump  wagons — Surface 

grader — Road  leveler — Draining  tools 137 

The  Earth-road  Drag:  Requisites  for  success — Description  of  drag 
— Object  of  road  dragging — Theory  of  road  dragging — Effect 
of  dragging  roads — Instructions  for  dragging — Conclusion 145 

CHAPTER  VIII— BROKEN-STONE   ROADS 

Difference  between  methods  of  Telford  and  Macadam — John  Loudon 
Macadam — Thomas  Telford — Tresaguet's  method — Telford 's 
method — Macadam's  method — Modern  telford  and  macadam 
— Defects  of  telford  system — Defects  of  macadam  system 
— Advantages  and  defects  of  broken-stone  pavements — Diffi- 
culties in  construction — Essentials  for  successful  construction — 
Errors  in  construction — Materials — Dimensions  of  the  macadam 
surface — Subgrade — First  course — Second  course — Third  course 
— Trimming — Rolling — What  holds  macadam  roads  together — 
Steam  rollers — Breaking  stone — Stone  crushers — Stone  crushing 
plant — Stone  distributing  carts — Scarifiers — Straight-edge — 
Water  carts — Cost  of  macadam  surfaces 154 

CHAPTER   IX— ROADS   IN  MOUNTAINOUS   DISTRICTS 

Evolution  of  mountain  roads — Grade — Importance  of  location 
— Object  of  drainage — Necessity  for  proper  side  slope — Width 
— Curves — Slide  rock — Corduroy — Dressing 189 

CHAPTER   X.    IMPROVEMENT  AND   MAINTENANCE   OF 
COUNTRY  ROADS 

Reconstruction    and    Improvement:     Defects    of     existing    roads — 

Benefits  of  improvements — Clay  roads — Sand  roads 203 


CONTENTS  xi 

PAOB 

Maintenance  and  Repairs:  Necessity  for  maintenance — Systems 
of  maintenance — Maintenance  of  country  roads — Errors  in 
maintenance — Cost  of  maintenance — Causes  which  make  re- 
pairs necessary — Repair — Instructions  to  roadmen — Season  for 
repairs 205 


CHAPTER  XI.  CONTROL  AND  PREVENTION  OF  ROAD 

DUST 

Importance  of  dust  prevention — Value  and  effects  of  road  dust 
— Effects  of  automobile  traffic — Necessity  for  dust  prevention 
— General  results  of  experiments — Methods  of  dust  prevention — 
Moisture — Salt  water — Calcium  chloride — Oil  emulsions — Oils — 
Inexperience  in  handling  road  oils — General  rules  for  oiling  roads 
— Coal-tar  preparations — Success  of  "  tarviating  " — Tar-spraying 
machines — Tests  of  coal-tar — Tar-macadam — Mixing  tar-mac- 
adam— The  "  Glad  well "  system — Use  of  tar-macadam  in  America 
— Rock  asphalt  macadam — Bitulithic  pavement 218 


CHAPTER   XII.     STATE   AID    LAWS 

Distribution    of    State-aid    funds — Supervision    of    construction — 

Form  of  commission 248 

DIGEST  OF  STATE- AID  LAWS: 

State  Highway  Department — State  Aid  Highways — State  Aid 
Fund — Powers  and  Duties  of  Counties — County  or  District 
Highway  Engineers — How  Localities  get  State  Aid — Construction 
of  State  Aid  Highways — Payment  for  State  Aid  Highways — Main- 
tenance of  State  Aid  Highways 252 

Convict  Labor  on  Roads 271 

Excerpts  from  Specifications  used  in  Constructing  State-aid  Roads  in 
Massachusetts,  New  Jersey,  New  York,  Connecticut,  Pennsylvania 
and  Maryland 272 


PART   III 

CITY   STREETS   AND    PAVEMENTS 
CHAPTER  XIII.    THE   DESIGN   OF  CITY  STREETS 

Objects  in  planning  city  streets — Size  of  blocks — Location  of 
streets — General  plans  for  location  of  streets — Width  of  streets 
Area  of  streets — Width  of  pavement — Driving  in  middle  of  road 
destructive — Center  walks  instead  of  sidewalks. .  ...  296 


xii  CONTENTS 

CHAPTER  XIV.    STONE   BLOCK   PAVEMENTS 

PAGB 

Roman  roads — Cobblestone  pavement — Belgian  block  pavement — 
Granite  block  pavement — Advantages  and  defects — Quality 
of  the  stone — Size  and  shape  of  the  blocks — Manner  of  laying 
the  blocks — Foundation — Laying  the  blocks — Joint  filling — 
Pavements  on  steep  grades — Durability  of  granite  blocks 311 

CHAPTER  XV.     BRICK   PAVEMENTS 

Advantages  and  defects — Quality  of  brick — Brick-clay — Region  of 
production — Manufacture  of  paving  bricks — Size  and  shape 
of  bricks — Testing  bricks — Construction  of  pavement — Manner  of 
laying  bricks — Durability 323 

CHAPTER   XVI.     WOOD    BLOCK   PAVEMENTS 

Progress  of  wood  paving — Woods  used  for  paving — Qualities  of 
treated  wood  pavement — Cost — Service — Durability — Tractive 
resistance — Quality  of  wood  used  for  paving — Wood  preserving 
methods — Creosoting — Impregnation  of  timber — Kreodone-creo- 
sote  process — Creo-resinate  process — Foundation  and  cushion — 
Blocks — Angle  of  courses — Expansion  joints — Filler — Top  dress- 
ing— Repairs  and  maintenance 335 

CHAPTER   XVII.     ASPHALT   PAVEMENTS 

Nomenclature  —  Bitumen  —  Asphalt  —  Historical  —  European  and 
American  pavements — Artificial  sheet  asphalt  pavement — Dur- 
ability   357 

Construction  of  the  Pavement:  Foundation — Binder  course — Com- 
position of  wearing  surface — Mixing  and  spreading  wearing 
surface — Failures  of  asphalt  pavements — Repairs 365 

Asphalt  Block  Pavement:    Manufacture — Advantages  and  defects. .  .   376 

Coal-tar  Pavements:   Coal-tar  and  asphalt — Advantages — Defects.  .  .   377 

CHAPTER   XVIII.     CONCRETE   PAVEMENTS 

Advantages  of  concrete — First  cost — Cost  of  maintenance — 
Ease  of  traction — Foothold — Noiselessness — Cleanliness  and 
healthfulness — Acceptability — Construction — Hassam  pavement 
— Materials — Method  of  Work — Proportioning  materials — Mix- 
ing— Topping  and  finishing — Road  surface  of  concrete  cubes — 
Concrete  block  trackway 380 

Concrete  Foundations .   399 


CONTENTS  xiii 

CHAPTER  XIX.     THE  CLEANING  AND  SANITATION  OF  CITY 

STREETS 

PAGE 

Early  history  of  street  cleaning — Municipal  growth  in  America 
— Uses  of  city  streets — Sources  of  street  dirt — Reasons  for  un- 
clean streets — Aim  of  sanitation — Cooperation  required — Varie- 
ties of  city  waste — Comparative  cleanliness  of  pavements — 
Orderlies — Machinery  employed  in  street  cleaning — Street  clean- 
ing authority — Organization  of  forces — Flushing — Disposal  of 
street  dirt — Removal  of  household  refuse — Summary 401 


CHAPTER  XX.    SIDEWALKS,  CURBS,  AND  GUTTERS 

Width — Slope — Foundation — Requirements  of  a  good  walk — 
Materials  used — Sandstone — Granite — Wood — Brick — Artificial 
stone — Gravel — Cement  and  concrete — Sub-foundation  and  drain- 
age— Upheaval  by  tree  roots — Foundation — Concrete  base — Top 
Coat— Joints 424 

Standard  Specifications  for  Portland  Cement  Concrete  Sidewalks  of  the 

National  Association  of  Cement  Users 441 

Curbs  and  Gutters:  444 


CHAPTER    XXI.     MISCELLANEOUS    ROADS    AND    PAVEMENTS 

Stone  trackways — Steel  trackways — Concrete-block  trackways — 
Artificial  granite  blocks — Plank  roads — Corduroy  roads — Char- 
coal— Slag  roads — Coal-slack  roads — Clinkers — Destructor  con- 
crete— Shell  roads — Cork — Copper  slag — India  rubber — Artificial 
paving  stones — "  Durax  "  roads 450 


CHAPTER  XXII.     THE   ROADSIDE 

Hedges     and    fences — Trees — Selection     of     trees — Planting — Tree- 
planting  Association 463 


APPENDIX 

I.  SPECIFICATIONS  AND  CONTRACTS 473 

II.  PAVEMENT  GUARANTEES 487 

III.  CONCERNING  THE  WEAR  OF  ROADS  BY  AUTOMOBILES 491 

IV.  STATISTICS  OF  AMERICAN  ROADS 499 

V.  BIBLIOGRAPHY  OF  ROADS,  STREETS,  AND  PAVEMENTS 505 

INDEX.  .  535 


THE   ROAD* 

Soon  as  I  knew  you  gathered  from  all  lands, 

And  that  my  cause  was  in  your  skilful  hands, 

My  pulses  gave  one  throb  and,  with  a  bound, 

To  be  with  you  I  quitted  all  my  ground, 

City  and  village,  forest,  hill  and  plain, 

And,  Phryne  at  the  judgment  once  again, 

My  veil  of  dust  hiding  the  fears  you  gave  me, 

Behold  me  at  your  feet,  my  masters!     Save,  oh  save  me! 

Oh  save  me,  when  I  wander  o'er  the  plains 

Or,  'twixt  the  hedges  of  the  country  lanes, 

I  stretch  my  arms  beneath  some  leafy  glade, 

Heavy  with  sleep  and  flecked  with  sun  and  shade; 

When  like  a  serpent  undulate  I  glide, 

Trailing  my  white  robe  up  the  mountain's  side; 

When,  drunk  with  light,  for  breezes  fresh  I  look 

And  wind  along  some  chattering  brook; 

When  I  plunge  into  chasms,  sound  the  deeps, 

Climb  to  the  plateaux,  mount  the  dizzy  steeps; 

Or  when  above  the  mountains,  near  the  skies, 

I  spread  new  worlds  before  men's  dazzled  eyes 

For  all  the  gifts  on  you  I  have  bestowed, 

Be  my  good  doctor — save,  oh  save  the  Road ! 

My  case  is  grave  and  needs  swift  remedy; 
Never  has  greater  peril  threatened  me — 
True,  as  in  France,  so  in  all  other  climes, 
Much  have  I  suffered  from  most  ancient  times. 
In  days  when,  sometimes  subject,  sometimes  free, 
People  met  people  in  fierce  enmity, 
I  bore  the  shock  of  many  a  battle  train 
Rushing  to  doubtful  death  or  doubtful  gain; 
And,  like  some  avalanche  of  myriad  tons, 
The  murd'rous  passage  of  the  heavy  guns. 


*  Translation  of  an  anonymous  poem  recited  by  Mme.  Bartet  at  the  Gala  Per- 
formance given  at  the  Comddie  Francaise  on  Oct.  14,  1908,  in  honor  of  the  First 
International  Road  Congress,  Paris.  Reprinted  from  "The  First  International  Road 
Congress,  Paris,  1908."  By  G.  M.  Harris  and  H.  T.  Wakelam. 

xiv 


THE   ROAD  XV 


Chanting  the  Marseillaise,  thirsting  for  war 
A  nation  shod  with  sabots  passed  me  o'er, 
And  the  great  Emperor,  to  spread  his  fame 
Over  a  world  which  trembled  at  his  name, 
Compelled  me  to  his  will  and,  spurring  fast, 
Triumphant  o'er  my  prostrate  body  passed. 
Glory  I've  borne — a  heavy  load  to  bear! 
And  others  too  as  heavy  and  less  fair; 
The  clumsy  cart,  rumbling  with  jolt  and  jar 
Has  crushed  my  bosom,  leaving  many  a  scar; 
Coach,  post-chaise,  and  postilions  in  full  cry, 
Flayed  my  back  sorely,  as  they  galloped  by. 

The  lumber  wagon  laid  my  sinews  bare! 
Yet  I  stood  firm,  defying  wear  and  tear, 
Even  I  thought  to  breathe  with  greater  ease; 
My  toil,  less  burdensome,  began  to  please. 
No  longer  coach  or  post-chaise  o'er  me  whirled, 
I  was  forgot,  abandoned  by  the  world. 
Rarely  some  cart  with  tranquil  pace  would  creep 
Me  by,  the  lazy  driver  half  asleep — 
Nought  else  by  day  or  night  disturbed  my  rest, 
Thus,  by  sweet  dolce  far  niente  blessed, 
Thinking  my  woes  forever  passed  away, 
In  a  false  calm  I  lived  until  one  day — 

A  terrible  monster  burst  into  sight, 
God  knows  from  out  of  what  hell  'twas  cast. 
Sheathed  all  in  iron,  a  thing  of  might, 
Swiftly  it  passes — it  has  passed! 

It  has  passed,  with  a  fearsome  hooting, 
Trail  of  smoke  and  a  sudden  glare, 
Like  to  some  dazzling  meteor  shooting 
Over  the  highways  of  the  air. 

Fast  and  furious,  onward  dashing 

Tow'rds  an  horizon  which  e'er  shrinks  back; 

Fiery  bolts  of  lightning  flashing 

Over  an  echoing  thunder  track! 
f~ 

And  ah!   for  me  it  means  a  wound  indeed, 

My  face  is  crushed,  my  sides  their  binding  bleed, 

Car  after  car  make  ever  fresh  attacks, 

Till  my  macadam's  nought  but  ruts  and  cracks. 


XVI  THE    ROAD 

My  body  thus  commences  to  decay 
And,  into  dust  dissolving,  floats  away! 
Must  I  then  die? 

No,  no!   For  you  are  here; 
With  you  to  aid  me  I  have  nought  to  fear. 
Science  and  genius  are  in  you  allied ! 
In  your  great  wisdom  I  can  well  confide. 
Quitting  the  beaten  paths,  you'll  seek  new  ways 
Towards  the  cure  for  which  your  suppliant  prays, 
Thresh  out  fresh  doctrines,  find  the  golden  mean 
And,  to  preserve  the  route  avoid  routine! 

Your  patient's  at  your  feet,  apply  your  skill, 

Probe,  sound,  investigate  me  as  you  will, 

And,  to  prevent  the  tortures  of  the  past, 

Perfect  a  work,  my  masters,  that  will  last! 

Do  this,  and  grateful  evermore  will  be 

All  travelers — nay,  all  humanity; 

For  'tis  the  road  that  is  the  fertile  way, 

Where  Life  and  Progress  must  forever  stray; 

Where,  seeking  space  and  beauty  far  and  wide, 

The  tourist  flings  unnumbered  miles  aside, 

And  over  hills  and  valleys  sows  the  seed 

Which  shall  bring  forth  abundance  in  our  need! 

And  when  at  length  you  have  achieved  your  aim, 

Restored  my  health  and  strengthened  all  my  frame; 

When  by  your  work  you've  made  me  proof  to  shock, 

Fearless,  invulnerable,  firm  as  rock; 

My  youth  renewed,  and  more  than  ever  fair, 

I'll  sing  your  praise  here,  there  and  everywhere; 

Beneath  all  skies,  telling  the  joyful  story, 

At  every  cross-roads  I'll  proclaim  your  glory 

On  Touring  Club  sign-posts  for  all  to  see! 

The  surest  road  to  Immortality! 


ADDENDA. 

Page  23.  It  should  be  added  to  the  last  paragraph  that  some  of  the 
States  have  created  and  financed  Highway  Commissions,  as  is  detailed 
on  Page  252. 

It  should  also  be  added  that  New  York  State  has  classified  its  roads 
as  follows: 

2,800  miles  of  main  roads  across  the  State  from  N.  to  S.  and  E.  to  W., 
known  as  "  State  "  Roads,  to  be  built  and  maintained  at  cost  of  State 
and  by  the  State. 

7,500  miles  of  main  "  County  "  roads,  being  the  most  important  roads 
in  the  47  Counties  to  be  improved  by  the  State,  which  pays  50%,  the 
County  paying  35%  and  the  Town  15%. 

70,000  miles  of  "  Town  "  roads  to  be  improved  as  earth  roads  under 
State  supervision,  at  the  expense  of  the  Towns,  plus  an  equal  sum  to  ba 
donated  by  the  State  as  "  State  Aid." 

Page  24.  In  reference  to  the  last  paragraph,  while  the  Massachusetts 
State  Highway  Commission  is  one  of  the  most  important,  at  the 
present  time  the  most  important  highway  undertaking  is  probably 
that  of  the  New  York  State  Highway  Commission,  which  is  charged  with 
the  expenditure  of  the  proceeds  of  fifty  million  dollars'  worth  of  bonds, 
having  taken  from  the  State  Engineering  Department  the  charge  of  High- 
ways in  February,  1909. 

Until  about  1902  the  Massachusetts  Highway  Commission  was  the 
most  important  State  organization,  the  other  States  (including  New 
York)  learning  much  from  the  experience  and  good  work  in  Massachusetts 
and  meantime  exceeding  them  in  mileage.  The  mileage  of  New  York  was 
about  520  miles  in  1909,  while  the  Massachusetts  Commission  reports 
show  their  annual  new  mileage  as:  47  miles  finished  in  1907,  38  miles 
built  in  1908,  and  about  45  miles  in  1909. 

xvii 


THE  ART  OF  ROADMAKING 


INTRODUCTION 
HISTORICAL  SKETCH   OF  ROAD   DEVELOPMENT* 

THE  word  "Road"  (Anglo-Saxon  rad,  a  riding,  and  ridan, 
to  ride)  is  commonly  used  to  mean  a  public  highway,  but 
custom  has  applied  it  to  any  kind  of  a  path  open  to  foot  or 
vehicular  traffic.  In  the  most  ancient  times  there  were 
no  roads.  The  wants  of  man  were  few  and  were  easily 
satisfied  by  nature  and  his  knowledge  and  intercourse  were 
limited  to  his  immediate  vicinity.  But  as  the  population  of 
the  various  communities  multiplied,  and  with  it  the  neces- 
sities of  life,  man  was  led  further  afield  to  supply  them.  He 
formed  rough  pathways,  which,  in  time,  came  to  be  the 
recognized  routes  from  one  locality  to  another,  by  means 
of  which  he  satisfied  his  desire  for  investigation  and  inter- 
course with  his  neighbors,  for  the  products  of  other  localities, 
and  for  conquest. 

"Countries  inhabited  by  the  least  civilized  people,  whose 
wants  can  be  supplied  in  the  immediate  vicinity  of  their 
dwellings,  are  almost  destitute  of  roads;  hence  it  has  come 
to  be  said  that  roads  are  the  physical  symbol  by  which  to 
measure  the  progress  of  any  age  or  people.  'If  the  community 
is  stagnant,  the  condition  of  the  roads  will  indicate  the  fact; 
if  they  have  no  roads,  they  are  savages.'"  f 

*  The  majority  of  current  books  on  the  subject  of  roads  open  with 
an  introductory  historical  chapter,  but  the  most  comprehensive  general 
histories  may  be  found  in  Byrne's  "Treatise  on  Highway  Construction," 
and  Tillson's  "Street  Pavements  and  Paving  Materials,"  and  the  best 
as  applied  to  British  Roads  in  Aitkin's  "Road  Making  and  Maintenance." 

t  Byrne:  "Highway  Construction." 

1 


2  THE  ART    OF  ROADMAKING 

Roads  are  not  only  the  offspring  of  civilization,  but  they 
are  also  the  greatest  contributors  to  it  and  the  greatest  factors 
in  its  advancement. 

Without  them  the  arts  that  are  so  beneficial  and  necessary 
to  the  welfare  of  man  could  not  develop;  the  interchange  of 
ideas  and  the  advantages  that  result  therefrom  could  not 
be  maintained;  in  fact,  the  civilization  of  to-day  with  its 
large  cities  and  towns,  its  commerce,  newspapers,  and  its 
highly  developed  moral,  physical,  and  intellectual  life,  could 
not  exist  at  all. 

One  of  the  very  first  steps  in  the  opening  up  of  a  new 
country  is  the  location  and  building  of  roads  for  the  accom- 
modation of  travelers,  the  carriage  of  commodities,  and  for 
the  development  of  the  natural  resources  and  manufactures 
of  the  country.  Smiles,  in  his  "  Lives  of  the  Engineers/7  says: 
"The  road  is  so  necessary  an  instrument  of  social  well-being, 
that  in  every  new  colony  it  is  one  of  the  first  things  thought 
of.  ...  The  new  country,  as  well  as  the  old,  can  only  be 
effectually  opened  up,  as  the  common  phrase  is,  by  roads, 
and  until  these'  are  made  it  is  virtually  closed." 

Of  the  early  history  of  road  building  as  of  other  works 
done  in  the  early  life  of  the  human  race,  little  is  known; 
while  no  authentic  records  exist,  it  is  known  that  the  import- 
ance of  good  roads  was  recognized  in  very  ancient  times. 
We  are  told  by  Herodotus  of  a  stone  roadway  built  by  King 
Cheops  about  4000  B.C.,  over  which  were  conveyed  the  heavy 
materials  for  the  construction  of  the  great  Egyptian  pyramid 
that  bears  his  name.  We  are  also  told  of  a  broad  roadway 
connecting  the  ancient  city  of  Memphis  with  the  pyramids 
and  lined  on  both  sides  with  temples,  mausoleums,  porticos, 
monuments,  etc.  Later  historians  tell  us  of  the  pavements 
of  Babylon,  of  many  paved  roadways  diverging  from  that 
city  and  of  a  highway  connecting  Babylon  and  Memphis  and 
passing  through  the  great  commercial  cities  of  Nineveh, 
Palmyra,  Damascus,  Tyre,  and  Antioch.  It  is  to  the  Carthe- 
genians,  however,  that  credit  must  be  given  for  the  earliest 
systematic  and  scientific  efforts  at  road  building,  for  as  early 
as  the  fifth  century  B.C.  they  had  developed  a  system  of 


INTRODUCTION  3 

communication  and  military  power  that  enabled  them  to 
maintain  their  integrity  against  Greece  and  the  Roman 
Empire  for  four  hundred  years.  The  Romans  learned  the 
art  of  road  building  from  the  Carthagenians,  and  so  fully  did 
they  appreciate  the  military  advantages  of  improved  high- 
ways that  they  soon  became  the  greatest  road  builders  of 
history. 

The  first  Roman  road  of  which  we  have  historical  evidence 
was  built  in  312  B.C.  by  Appius  Claudius,  the  censor,  and 
was  named  after  him — the  Appian  Way.  Some  years  later, 
the  Flaminian  Way  was  built,  and  under  Augustus  and  Julius 
Csesar  and  succeeding  emperors,  Rome  was  made  the  center 
of  a  wonderful  system  of  paved  roadways  stretching  out  to 
all  parts  of  its  great  empire.  These  reached  through  Italy, 
Gaul,  and  Spain;  through  Germany,  Hungary,  Macedonia; 
to  the  islands  of  Sicily,  Corsica,  Sardinia,  England,  and  to 
Africa  and  Asia  Minor  and  the  East;  in  all,  a  system  of  372 
roads,  which,  according  to  Antoninus,  amount  to  a  total 
length  of  52,964  Roman  miles. 

It  is  said  that  for  a  distance  of  fifty  miles  from  Rome  many 
of  these  roads  were  decorated  with  temples  and  other  superb 
edifices;  lodging  houses  for  the  accommodation  of  couriers 
and  mansions  for  soldiers  were  erected  at  regular  intervals 
at  the  public  expense.  The  width  of  these '  military  roads 
was  from  36  to  40  Roman  feet,  the  middle  portion  being  for 
the  infantry,  and  the  margins  for  horses  and  carriages.  Many 
miles  of  these  roads  still  remain  as  great  monuments  to  the 
energy  and  skill  of  the  Romans,  and  show  the  truth  of  the 
familiar  saying  that  "All  roads  led  to  Rome." 

Not  far  behind  the  Romans  in  the  art  of  road  building  were 
the  ancient  Incas  of  Peru,  who  built  some  thousands  of 
miles  of  good  roads  in  the  face  of  great  difficulties.  In  his 
"History  of  Peru,"  Prescott  says  of  the  mountain  road  from 
Quito  to  Cuzco:  "It  was  conducted  over  sierras  covered  with 
snow;  galleries  were  cut  through  the  living  rock;  rivers  were 
crossed  by  means  of  bridges  swung  suspended  in  the  air; 
precipices  were  scaled  by  stairways  hewn  out  of  the  native 
bed,  and  ravines  of  hideous  depth  were  filled  up  with  solid 


4  THE  ART  OF   ROADMAKING 

masonry."  Most  of  this  roadway  was  built  at  an  elevation 
of  12,000  feet  above  the  sea;  it  was  more  than  1500  miles 
long  arid  20  feet  wide;  paved  with  stones  10  feet  square  and 
had  a  running  stream  and  a  row  of  shade  trees  on  each  side. 

After  the  decline  of  the  Roman  Empire,  the  roads  fell  into 
disuse  and  during  the  succeeding  dark  ages  they  were  used 
more  as  aids  to  plunder  and  violence  than  for  purposes  of 
legitimate  intercourse.  Later  they  became  practicable  for 
pack  horses  and  rude  vehicles,  but  no  effort  was  made  to 
restore  them  until  the  middle  of  the  eighteenth  century  when 
a  revival  of  road  building  arose  simultaneously  in  England 
and  France.  The  highways  of  England  at  that  time  were 
wretched  beyond  description  and  an  effort  was  made  to  improve 
this  condition  by  the  establishment  of  a  system  of  turnpikes. 
Many  thousands  of  miles  of  these  roads  were  built,  but  they 
were  little  or  no  improvement  over  the  old  roads,  and  no 
further  advance  was  made  until  the  time  of  Macadam  and 
Telford,  to  whom  England  is  indebted  for  her  present  admir- 
able system  of  roads. 

In  the  United  States  the  highways  are  much  inferior  to 
those  of  European  countries,  the  reason  for  which  Byrne  * 
states  may  be  attributed  to  (1)  the  excellence  of  the  railroad 
systems  and  waterways;  (2)  the  indifference  of  those  in 
charge  of  highway  maintenance;  (3)  the  want  of  appreciation 
of  the  benefits  of  good  roads  and  the  fear  of  increased  taxation 
on  the  part  of  the  rural  population;  (4)  the  dispersion  of 
the  people  over  large  areas  in  their  search  for  desirable 
localities  for  residences,  and  (5)  the  ill-effects  of  the  system 
requiring  the  personal  services  of  the  rural  population  on  the 
highways. 

The  first  inhabitants  of  this  country  were  too  fully  occupied 
in  subduing  the  wilderness,  establishing  homes,  opening 
farms  to  provide  the  necessaries  of  life,  and  setting  up  the 
framework  of  a  government,  to  give  much  attention  to  the 
conveniences  and  comforts  of  transportation;  and  hence 
their  wagon  roads  were  of  the  crudest  and  poorest  sort. 

*  "Highway  Construction. "p.  xxxviii. 


I 

& 

.= 


llC 


a 
I 


INTRODUCTION  5 

Later,  just  as  an  extension  of  the  population  to  the  West 
necessitated  the  development  of  better  means  of  transporta- 
tion, the  introduction  of  the  railroad  made  less  important 
the  wagon  roads  and  engrossed  the  attention  of  the  popu- 
lation of  the  new  territory.  In  a  large  part  of  the  United 
States  the  railroad  has  been  the  pioneer  and  has  rendered 
unnecessary  long  lines  of  wagon  transportation.  At  present 
the  country  is  so  well  supplied  with  excellently  managed 
railroads  that  the  chief  function  of  the  wagon  road  is  to 
afford  easy  communication  and  transportation  between 
neighboring  farms,  and  between  the  farm  and  the  nearest 
railroad  station.  Thus  the  problem  of  good  roads  had  become 
a  local  question,  both  with  respect  to  the  community  the 
road  serves  and  to  the  materials  and  methods  most  suitable 
for  use  in  the  construction. 

These  facts  relate  to  roads  as  distinguished  from  pavements, 
or  road  surfaces.  The  date  of  the  introduction  of  pavements 
is  very  indefinite.  In  his  "History  of  Inventions  and  Dis- 
coveries/' John  Beekmann,  professor  in  the  University  of 
Gottingen,  devotes  a  chapter  to  the  paving  of  streets,  and 
from  his  historical  sketch  the  following  more  interesting 
points  are  taken: 

"  While  Roman  writers  of  early  date  often  refer  to  paved 
highways  and  especially  describe  the  famous  Appian  Way, 
of  312  B.C.,  there  is  comparatively  little  reference  to  the 
paving  of  streets  in  cities.  The  streets  of  Thebes  were 
regularly  cleaned  under  the  inspection  of  Telsarchs,  and  it 
is  to  be  assumed  that  they  were  paved;  and  the  Talmud 
says  that  the\streets  of  Jerusalem  were  swept  every  day, 
which  undoubtedly  implies  a  hard  and  solid  pavement.  There 
is  no  record  of  the  first  street  pavement  in  Rome;  but  Livy 
mentions  that  certain  streets  were  ordered  to  be  paved  in 
169  B.C.,  and  as  early  as  530  B.C.  the  Emperor  Heliogabulus 
paved  the  streets  around  the  palace  with  foreign  marble. 
The  streets  of  Pompeii  and  Herculaneum  still  show  their 
paving  blocks  of  lava,  cut  into  deep  ruts  by  the  wheels  of 
passing  chariots. 

"Passing  to  later  times,  we  find   the  streets  of  Cordova, 


6  THE  ART    OF    ROADMAKING 

in  Spain,  paved  as  early  as  A.D.  850,  by  order  of  the  Caliph, 
Abderrahman  II.  The  first  record  of  any  street  paving  in 
Paris  is  dated  in  the  year  1184,  when  the  name  of  the  city 
was  changed  from  'Lutetia/  the  dirty,  to  'Paris/  This 
innovation  is  said  to  have  arisen  from  the  fact  that  the 
King,  Philip  II,  was  annoyed  by  the  offensive  odors  produced 
by  the  agitation  of  the  mud  in  front  of  his  palace  by  passing 
vehicles.  He  resolved  to  remedy  the  intolerable  nuisance  by 
ordering  the  streets  paved,  and  succeeded  in  having  this  done, 
in  part,  at  least,  notwithstanding  the  heavy  cost,  which  had 
deterred  his  predecessors. 

"In  1090  the  streets  of  London  were  soft  earth  only;  but 
when  the  first  pavement  was  introduced  is  not  known. 
Holborn  was  paved  for  the  first  time,  by  royal  command, 
in  1417;  Henry  VIII  ordered  other  streets  paved,  and  the 
great  market  square  of  Smithfield  was  first  paved  in  1614. 
Augsburg,  in  Germany,  seems  to  have  been  the  first  city 
in  that  country  to  introduce  footways  and  street  pavement, 
in  1415,  but  the  extension  of  the  improvement  to  other 
towns  was  slow,  and  the  streets  of  Berlin  were  not  all  paved 
even  in  1679." 

In  the  United  States,  Boston  was  the  first  place  to  pave 
its  streets — pebbles,  cobblestones,  and  flagging  being  used 
during  the  seventeenth  century.  In  New  York  city  the  first 
stone  pavement  was  laid  about  1657  on  what  is  known  to-day 
as  Stone  Street,  and  the  first  sidewalks  were  laid  in  1790, 
on  the  west  side  of  Broadway. 

Toll  roads  were  first  constructed  in  England  in  1346,  and 
were  built  until  1878,  when  they  were  entirely  abolished. 
In  1792  a  toll  road  company  was  incorporated  in  Pennsylvania 
to  construct  and  maintain  an  artificial  road  from  Philadelphia 
to  Lancaster.  In  1834,  the  Albany  and  Schenectady  turn- 
pike was  laid  with  stone  wheel-tracks  for  a  distance  of  fourteen 
or  sixteen  miles.  The  turnpike  itself  was  made  in  1805, 
of  gravel,  at  a  cost  of  $8400  per  mile.  Ten  years  later  a 
"sunken  pavement"  of  cobblestones  was  built  on  the  dry 
and  sandy  parts  of  the  road,  and  broken  quarry  stone,  to  the 
depth  of  twelve  inches,  was  bedded  in  the  wet  and  clayey 


INTRODUCTION  7 

parts,  the  edges  bonded  by  lines  of  small  boulders  imbedded 
in  the  earth  along  each  side. 

In  1831  protests  were  made  by  the  stockholders  of  this 
turnpike  company  against  the  effect  of  the  charter  granted 
to  the  Mohawk  &  Hudson  Railroad  Company,  on  the  ground 
that 

"Should  the  railroad  company  succeed,  their  operations 
will  necessarily  diminish  materially  the  tolls  of  the  turnpike 
company,  and  thus  sap  the  consideration  upon  the  faith  of 
which  the  latter  have  constructed  their  road." 

Referring  to  the  application  of  the  railroad  company  for 
leave  to  run  a  side-track  into  the  heart  of  Albany,  Chancellor 
Kent  wrote: 

"If  that  would  not  be  an  interference  with  the  rights 
of  the  turnpike  company,  then  nothing  would  be  an  inter- 
ference short  of  plowing  up  the  turnpike  road." 

It  was  feared  that  the  railroad  might  eventually  displace 
the  stages,  the  tolls  from  which  formed  a  large  portion  of  the 
revenues  of  the  previously  chartered  turnpike  company,  but 
the  steam  railroad  was  built,  and  was  opened  to  operation 
on  September  12,  1831,  as  the  first  exclusively  passenger 
railroad  in  the  world.  The  handling  of  freight  by  the  rail- 
road was  not  begun  until  December  6,  1832,  when  three 
cords  of  wood,  making  two  carloads,  were  taken  to  Albany, 
and  were  the  first  freight  carried  on  what  is  now  the  New 
York  Central  Railroad.  In  order  to  compete  with  the  nul- 
road,  the  turnpike  company  then  made  many  efforts  to 
arrange  to  build  another  railroad  of  their  own  along  the 
side  of  the  turnpike,  and  the  failure  of  these  efforts  resulted 
in  deciding,  in  1832,  to  lay  the  "stone  rails,"  of  which  twenty 
thousand  linear  feet  were  laid  in  1833  and  1834,  at  a  cost, 
including  the  cobble  paving  between  the  tracks  and  the 
forming  of  the  roadbed,  of  $3300  per  mile.  Sections  of  this 
stone  wheel-track,  in  some  cases  half  a  mile  or  more  in  length, 
are  still  in  good  condition  and  in  daily  use,  as  shown  in  the 
photograph  on  next  page,  made  in  1901. 

About  1862,  a  system  of  similar  wheel-track  roads  was 
built  in  Ulster  County,  N.  Y.,  as  a  toll-road  from  Kingston, 


THE  ART  OF  ROADMAKING 


6  ft.  of  large  cobble  pavement. 


18  in.  to  24  in.  wide, 
4  in.  to  5  in.  thick, 


ROAD  FROM  ALBANY  WEST  TO  SCHENECTADY,  N.  Y.,  1901. 
Built  by  Turnpike  Company  in  1834. 


Groove  worn 
6  in.  wide,  3  in.  deep. 

ROAD  WEST  FROM  KINGSTON,  ULSTER  Co.,  N.  Y.,  1902. 
Built  by  Turnpike  Company  in  1862, 

STONE  WHEEL-TRACKS. 
(From  Judson's  "  City  Roads  and  Pavements.1') 


INTRODUCTION  9 

eight  miles  up  the  Delaware  and  Ulster  Valley,  to  the  blue- 
stone  quarries  in  the  Catskill  mountains.  This  proved  to 
be  so  successful  that  branches,  and  other  roads  of  the  same 
sort,  were  soon  built  and  are  still  in  decreasing  use.* 

The  ease  of  traction  on  these  smooth  slabs  led  to  an  increase 
of  the  loads  drawn  upon  them,  until  eight  tons  has  been 
and  is  an  ordinary  load  for  two  horses  to  bring  from  the 
quarries  to  the  wharves  at  Kingston  and  Rondout,  while 
loads  of  twelve  to  fourteen  tons  are  drawn  by  three  horses, 
and  loads  of  seventeen  tons  actual  weight  have  sometimes 
been  drawn  by  four  horses.  These  great  loads  were  formerly 
carried  upon  narrow  tires  of  one  and  one-half  to  two  inches, 
which  speedily  cut  furrows  in  the  hard  stones,  so  that  slabs 
six  to  eight  inches  thick  were  cut  through  in  three  or  four 
years. 

*  Judson's  "City  Roads  and  Pavements." 


PART   1 
PRELIMINARY   CONSIDERATIONS 


CHAPTER  I 
RESISTANCE  TO  TRACTION 

BEFORE  taking  up  the  study  of  the  location  and  construc- 
tion of  roads,  it  is  necessary  for  the  reader  to  understand 
something  of  the  problems  connected  with  the  theory  of  road- 
making — the  obstructions  and  resistances  to  motion  to  be 
overcome  by  the  traffic  using  the  road,  the  financial  considera- 
tions involved  in  the  construction  to  insure  its  greatest  econ- 
omy, and  the  questions  that  confront  the  engineer  in  making 
roads  to  suit  the  many  different  uses  to  which  they  are  pat. 
These  problems  are  outlined  in  this  and  the  two  following 
chapters. 

THE  object  of  a  road  is  to  provide  means  of  transporta- 
tion of  persons  and  goods  with  the  least  possible  expenditure 
of  time  and  money.     This  economy  depends  upon 
a  road  °       ^ne  amount  of  resistance  to  easy  motion  offered 
by  the  road,  the  causes  and  effects  of  which  are 
matters  of  great  importance  in  determining  the  ruling  gradient 
to  be  adopted  on  a  proposed  road,  according  to  its  situation 
and  the  class  of  traffic  that  will  use  it. 

Resistance  to  traction  is  made  up  of: 

tractive0*  *"  Ax*6   ^riction'  wmcn   ig  nearly  constant  at  all 

resistance  velocities,  and    is    independent  of  the   con- 

dition of  the  surface  of  the  road. 

10 


RESISTANCE    TO    TRACTION 


11 


2.  Rolling   resistance,   due  to   collisions  with  irregularities 

of  the  surface,  and  to  the  penetration  or  sinking  of 
the  tire  in  the  roadway. 

3.  Gravity,  or  resistance  due  to  gradient. 

4.  Air  resistance,  varying  according  to  the  velocity  of  the 

wind,  the  area  of  the  surface  acted  upon,  the  velocity 
of  the  vehicle,  and  the  angle  or  direction  at  which  it 
impinges  against  the  plane  of  the  surface. 
The  tractive  force,  or  the  power  required  to  move  vehicles 
along  a  road,  is  variable,  depending  upon  the  conditions  of  the 
road  and  the  power  of  the  horse.     The  power  of    Power 
the  horse  varies  in  turn,  according  to  its  strength,    required  to 
weight   and   special  training,  the  speed  at   which    move 
it  travels  and  the  hours  of  work,  but  it  may  be 
taken  as  an  average  of  -^  of  the  load  on  a  level  macadamized 
road  in  good  repair,  varying  from  -fa  of  the  load  on  the  best 
roads  to  -fa  on  roads  with  a  badly  maintained  surface. 

Reliable  tests  have  been  made  to  determine  the  force  re- 
quired to  overcome  the  combined  resistances  of  the  vehicle 
and  the  road,  resulting  in  the  accompanying  table: 

TABLE  I 

STANDARD    TRACTIVE    RESISTANCE    OF    DIFFERENT   ROADS 
AND   PAVEMENTS* 


vehicles. 


Tractive  I 

Resistance. 

Lbs.  per  Ton. 

In  Terms  of  Load. 

Asphalt,  artificial  sheet  
Brick  .    .      . 

30  to    70 
15  to    40 

1/67    to  1/30 
1/133  to  1/50 

Cobble  stones 

50  to  100 

1/40    to  1/20 

Earth  roads,  ordinary  condition  . 

50  to  200 

1/40    to  1/10 

Gravel  roads  
Macadam  . 

50  to  100 
20  to  100 

1/40    to  1/20 
1/100  to  1/20 

Plank  road  
Sand   ordinary  condition  .  . 

30  to    50 
100  to  200 

1/67    to  1/40 
1/20    to  1/10 

Stone  block  . 

30  to    80 

1/67    to  1/25 

Steel  wheelway  

15  to    40 

1/133  to  1/50 

Wood  block:  Rectangular  
Cylindrical 

30  to    50 
40  to    80 

1/67    to  1/40 
1/50    to  1/25 

*  Baker:  "Roads  and  Pavements,"  p.  31. 


12  THE    ART    OF  ROADMAKING 

The  resistance  of  pavements  to  tractive  effort  has  recently 
been  investigated  in  the  city  of  Toronto,  Orit.,  and  reported 
to  the  Canadian  Society  of  Civil  Engineers  in  a 
Recent  ex-  paper  by  Mr.  A.  C.  D.  Blanchard.  All  experi- 
Fntractive  ments  were  made  with  a  good,  steady  team  of 
resistance,  horses,  weighing  2940  pounds,  and  drawing  a 
truck  weighing  2710  pounds,  with  a  load  of  8570 
pounds.  Between  the  horses  and  the  truck  there  was  placed 
a  standard  dynamometer  which  was  read  by  an  observer  on 
the  truck,  at  stated  distances  paced  and  called  out  by  the 
notekeeper  walking  alongside.  Observations  were  made  on 
wet  and  dry  streets  of  varying  grade  and  paved  with  asphalt, 
bitulithic,  brick,  cedar  block,  granite  block,  and  treated  wood 
block.  From  the  figures  so  determined  curves  have  been 
plotted  on  grade  of  street  as  an  abscissa  and  tractive  resistance 
as  an  ordina,te.  For  dry  streets  these  curves,  which  are 
straight  lines,  show  the  brick  paving  to  have  the  least  resist- 
ance, the  others  following  in  the  order:  treated  block,  bitulithic, 
cedar  block,  granite  block,  asphalt.  These  lines  all  show  a 
fairly  uniform  rate  of  increase  of  resistance  with  grade,  except 
that  the  granite  block  seems  to  increase  its  resistance  with 
grade  somewhat  more  sharply  than  the  others. 

On  wet  streets,  the  order  of  tractive  resistances,  beginning 
with  the  lowest  and  going  up  is:  bitulithic,  asphalt,  treated 
block  and  cedar  block.  Wet  brick  pavements  were  not 
tested.  The  wetness  of  the  streets  seems  to  show  small 
effect  on  the  resistive  powers  of  the  pavement.  The  high 
place  of  the  asphalt  in  the  list  of  dry  weather  record?  is 
due  to,  no  doubt,  the  fact  that  dry  weather  is  hot  weather 
and  the  asphalt  pavement  then  is  rather  a  soft  mass  into 
which  the  wheels  of  a  wagon  sink.  On  wet,  and  therefore 
cold  and  hard,  asphalt  pavements,  the  asphalt  shows  a  very  low 
resistance. 

The  tractive  force  required  to  overcome  obstacles  is  equal 

to  the  horizontal  force  required  to  raise  the  wheel 

Calculation   tne     height     of     the     obstruction     when     applied 

force*0          directly  to   the    axle,    and    may  be   calculated  as 

follows : 


RESISTANCE    TO    TRACTION 


13 


In    Fig.  1,    let    P  =  power    required    to    overcome    obstacle 

B,  acting  in  direction  AP,  with  the 
leverage  x. 

W  =  Weight,  or  Gravity,  resisting  in 
direction    WA,    with    leverage    y. 


• 


This  makes  an  equation  of  equilibrium 

Px  =  Wy,     or     P=WXy/x 
or  in  terms  or  radius  R,  where  z  =  height  of  obstruction 

P=W\/R2-x2/  (R  -z). 

'Example.     Let  radius  of  wheel  be  26  inches;   height  of  obstruction  be 
4  inches ;  and  the  weight  of  wheel  and  load  on  axle  be  500  pounds. 


Then  P  =  500  V676-- 484 / (26 - 4) ; 

=  500X^192/22; 

=  500X13.86/22  =314.9  pounds. 
The  pressure  at  point  B  =  WXR/x  =  500X26/22  =  591  pounds. 

mjl 

Rolling  friction  is  affected  largely  by  the  width  of  the  tires 
and  can  be  materially  decreased  by  increasing  their  width, 
a  tire  of  2J  inches  wide  causing  fully  double  the 
wear  of  one  4£  inches  wide.  The  only  exceptions  to 
this  are  in  cases  of 

1.  Hard  and  incompressible  surfaces,  where  width  makes 

little  difference   in   traction,   the   advantage   being 
in  favor  of  the  narrow  tire. 

2.  Sticky  and  dusty  surfaces,  where  the  large  quantity 

of  mud  and  dust  raised  by  the  wide  tires  increases 
the  draft. 
A  solid  rubber  tire    offers  slightly  less  resistance   than  an 


Rolling 
friction 


14  THE    ART    OF    ROADMAKING 

iron  one  if  the  road  is  wet  and  heavy,  but  more  if  the  surface 
is  hard  and  smooih.  Pneumatic  tires  reduce  tractive  re- 
sistance from  25  to  50  per  cent,  in  increasing  proportion  as 
the  road  grows  worse. 

The  size  of  the  wheel  also  has  much  to  do  with  tractive  re- 
sistance.    Acting  on  the  principle  of  a  lever,  small  wheels  in- 
crease,  and  large  wheels  decrease,  resistance,  pro- 
Effect  of        vided  the  diameter  of  the  wheels  is  not  so  great 
wheels  tna^   ^ne   ^me   °^   traction   will   be   downward   and 

consume  part  of  the  power  of  the  horse  by  pressing 
the  wheel  against  the  ground.  The  most  economical  size  of 
wheels  is  considered  to  be  about  six  feet  in  diameter. 

The  effect  of  springs  on  vehicles  is  to  diminish  the  wear 

on  roads,  especially  at  speeds  beyond  a  walking  pace.    Going 

at  a  trot,  they  cause  no  more  wear  than  vehicles 

s  dnV         without    springs   at   a   walk,    all   other    conditions 

being  equal. 
The  following  are  the  general  results  of  experiments  made 

by  M.  Morin  upon  the  resistance  to  traction  of 
General  re-  ,  .  ,  ,  ± 

suits  of         vehicles  on  common  roads :  * 

fnPtracTivetS      l"  The    resistance    to    traction    is    directly    pro- 
resistance      portional  to  the  load,   and   inversely  proportional 
to  the  diameter  of  the  wheel. 

2.  Upon  a  paved  or  a  hard  macadamized  road  the  resistance 
is  independent  of  the  width  of  the  tire,  when  this  exceeds 
from  3  .to  4  inches. 

3.  At  a  walking  pace,  the  resistance  to  traction  is  the  same, 
under   the    same    circumstances,    for    carriages    with    springs 
and  for  carriages  without  springs. 

4.  Upon  hard  macadamized  roads  and  upon  paved  roads, 
the  resistance  to  traction  increases  with  velocity — the  incre- 

*  Of  the  many  experiments  made  by  the  English,  German,  and  French 
engineers  on  the  force  necessary  to  pull  different  vehicles  at  various  speeds 
over  various  surfaces,  those  made  by  M.  Morin  in  1838-41,  seem  to 
have  been  the  most  extensive  series,  and  were  made  with  much  care  and 
a  high  degree  of  accuracy.  They  were  first  described  by  him  in  his 
"Experience  sur  le  tirage  des  Voitures,"  Paris,  1842,  and  have  been 
referred  to  by  nearly  all  modern  writers. 


RESISTANCE   TO  TRACTION 


15 


ments  of  traction  being  directly  proportional  to  the  increments 
of  velocity  above  the  velocity  of  3.28  feet  per  second,  or  about 
2\  miles  per  hour.  The  equal  increments  of  traction  thus 
due  to  equal  increments  of  velocity  are  less  as  the  road  is 
smoother,  and  as  the  carriage  is  less  rigid  or  better  hung. 

5.  Upon  soft  roads  of  earth,  sand,  turf,  or  roads  fresh  and 
thickly   graveled,   the   resistance   to   traction   is   independent 
of  the  velocity. 

6.  Upon  a  well-made  and  compact  pavement  of  hewn  stones, 
the  resistance  to  traction  at  a  walking  pace  is  not  more  than 
three-fourths  of  the  resistance  upon  the   best   macadamized 
roads,  under  similar  conditions.     At  a  trotting  pace  the  re- 
sistance is  equal. 

7.  The  destruction  of  the  road  is,  in  all  cases,  greater  as  the 
diameters  of  the  wheels  are  less,  and  it  is  greater  in  carriages 
without  than  in  those  with  springs. 

The  grade  of  the  road  is  the  quantity  by  which  it  differs  from 
the  level.  Theoretically,  all  roads  should  be  level,  and  where 
they  are  not  so,  a  large  portion  of  the  tractive  force  of  the  ve- 
hicles traveling  over  them  will  necessarily  be  expended 
in  raising  the  load  up  the  ascent.  This  resistance 
of  the  force  of  gravity,  or  weight  to  be  overcome,  is  the  same 
on  all  roads  in  any  condition,  and  is  in  all  cases  approximately 
equal  to  the  load  divided  by  the  rate  of  grade.  That  is,  the 
grade  resistance  on  any  incline  in  pounds  per  ton  is  2240/Rate 
of  Grade,  from  which  the  following  table  has  been  computed: 

TABLE  II 
RESISTANCE  DUE  TO  GRAVITY  ON  DIFFERENT  INCLINATIONS 


Gradient 


Grade,  1  in  

20 

30 

40 

50 

60 

70 

80 

90 

100 

200 

300 

400 

Rise  in  feet  per  mile  . 

264 

176 

132 

105 

88 

75 

66 

58 

52 

26 

17 

13 

Resistance  in  pounds 

per  ton  . 

112 

74* 

56 

45 

38 

32 

28 

25 

22 

Hi 

7i 

5| 

On  account'  of  this  loss  of  power  on  inclinations,  it  is  im- 
portant not  to  allow  a  road  to  ascend  or  descend  a  single  foot 
more  than  is  absolutely  unavoidable.  In  case  of  ascending 
a  hill,  the  road  should  be  so  located  and  have  such  cuttings 


16  THE  ART   OF    ROADMAKING 

and  fillings  as  will  secure  a  gradual  and  uninterrupted  ascent 
the  whole  way,  as  the  slightest  fall  would  make 

Loss  of          an  additional,  and  probably  a  steeper,  incline. 

inclinations  The  necessity  of  easy  gradients  is  dependent  upon 
the  power  of  the  horse  to  overcome  the  total  of 

the  four  elements  of  resistance  to  motion.  On  a  level,  smooth 
road,  the  pull  which  a  good  average  horse,  weighing 

10°°  to  12°°  P°unds>  can  exert  at  a  walking  pace, 
gradients  1S  about  100  pounds,  or  one-tenth  his  weight. 

A    1650-pound   horse    can   develop   the    conven- 
tional horse-power«of  550  foot-pounds  per  second  and  16,500,000 

foot-pounds  per  day  of  eight  and  one-third  hours, 

Hauling        which,  however,  may   be   considered   as  the    limit 

power  of 

horses  °f  endurance.     If  the  time  of  effort  is  decreased, 

the  draft  may  be  proportionately  increased,  and  vice 
versa.  The  maximum  draft  for  a  horse  is  about  half  his  weight, 
and  under  certain  conditions,  this  may  be  two-thirds,  but 
the  working  tractive  power  may  be  safely  taken  as  one- 
tenth,  with  an  average  maximum  of  one-quarter  the  weight, 
which  may,  in  great  emergencies,  be  increased  to  one-half. 

Increasing  the  number  of  horses  does  not  increase 
c        the  power  proportionately.     With  teams,  the  trac- 
tive power  is  about  as  follows: 

1  horse  .  . 1 

2  horses 0.95X2  =  1.90 

3  horses 0.85X3  =  2.55 

4  horses 0.80X4  =  3.20 

The  gross  load  that  can  be  drawn  by  a  horse  on  any  grade 


Calculation 
of  load  on 
a  gradient. 


B 


Fig.  2. 
can  be  approximately  calculated  by  the  formula: 


RESISTANCE  TO   TRACTION  17 

where    L  =  load  in  tons,  inclusive  of  vehicle, 
t  =  tractive  pull  of  horse  in  pounds, 
W  =  weight  of  horse  in  pounds, 
T  =  tractive  force  required  to  haul  one  ton  on  a  level 

(See  Table  I), 

72  =  rate  of  grade,  or  horizontal  distances  in  which  the 
rise  is  unity;   BC:AB.     (See  Table  II). 

Example.  What  load  can  a  good  horse,  weighing  1500  pounds,  haul 
on  an  ordinary  country  earth  road  (T=  150)  on  a  gradient  of  1  in  20, 
when  exerting  a  pull  of  200  pounds? 

L=  (200- 1500/20)  +  (150  +  2240/20) ; 
=  (200-75) -H150  + 112); 
=  125/262  =  .477,  or  about  $  torf. 

Actual  experience  has  shown  that  a  good  average  horse  can 
draw  on  a  level  earth  road  in  best  condition  a  load  of  about 
3600  pounds,  which  is  reduced  on  grades  as  follows: 


Pounds. 


1  per  cent  grade 2880 

2  "      "         "     2376 

3  "      "         "     1980 

4  •"  "         "                 .   1692 


Pounds 

5  per  cent  grade 1476 

10   "       "         "      936 

15   "       "         "      360 

20   "       "         "  144 


In  ascending  inclines  a  horse's  power  diminishes  rapidly.     A 
large  portion  of  his  strength  is  expended  in  over- 
coming the  resistance  of  gravity  due  to  his  own  Load  drawn 
weight  as  well  as  that  of  the  load;  also  by  fatigue  On  grades 
on  a  long  ascent  owing  to  his  anatomical  formation 
and  great  weight,  while  the  amount  of  foot-hold  afforded  by 
the  road  surface  seriously  affects  the  size  of  the  load  he  can  draw. 

Assuming  a  wagon  weighing  1200  pounds,  with  a  load  of  1800 
pounds,  amounting  to  3000  pounds,  the  force  of  gravity  on  a 
1  per  cent  grade  would  be  approximately  30  pounds, 

9       a        tt  a  u  u  u  /•/,         •- 

5     "      "         "  150       " 

10     "      "  300       " 

and  so  on,  being  always  constant,  regardless  of  the  condition 
of  the  road.  Steep  grades 

Steep  grades  are  thus  seen  to  be  objectionable,  objection- 
and  they  are  particularly  so  when  a  single  one  occurs  able- 


18 


THE  ART    OF  ROADMAKING 


in  an  otherwise  comparatively  level  road,  in  which  case  the 
load  carried  over  the  less  inclined  portions  must  be  reduced 
to  what  can  be  hauled  up  the  steeper  portion. 

Their  bad  effects  are  especially  felt  in  winter,  when  ice  covers 
the  road,  for  the  slippery  condition  of  the  surface  causes 
danger  in  descending,  as  well  as  increased  labor  on  ascending. 
Rain  water  runs  down  the  road  and  gullies  it  out,  destroying 
its  surface  and  causing  a  constant  expense  for  repairs,  while 
the  inclined  portions  are  subject  to  greater  wear  from  the  feet 
of  horses  ascending  and  require  thicker  covering  than  the 
more  level  portions,  thus  increasing  the  cost  of  construction. 

The  correct  determination  of  grade  is  of  the  utmost  im- 
portance in  road  building.  It  is  expressed  in  different  ways, 

generally  by  percentage.     A  1  per  cent  grade  means 
Methods  of    a   rige   of   1   foot   for   each    10Q  feet   of  horizontal 
expressing 
grade.  distance  traveled.      There  are  5280  feet  in  a  mile; 

hence,  a  1  per  cent  grade  means  a  rise  of  52.8 
feet  in  that  distance,  a  2  per  cent  grade  a  rise  of  105.6  feet, 
and  a  10  per  cent  grade  a  rise  of  528  feet. 

The  proper  grade  in  each  case  must  be  determined  by  the 
conditions  and  requirements.  This  selection  of  grade  is  further 
discussed,  in  its  relation  to  the  location  of  roads,  on  p.  45. 

TABLE  Ha 
VARIOUS   METHODS   OF   INDICATING   GRADE 


American 
Method. 
Feet  per 
100  Feet. 

English 
Method. 

Feet 
per  Mile. 

Angle  with 
the 
Horizon. 

American 
Method. 
Feet  per 
100  Feet. 

English 
Method. 

Feet 
per  Mile. 

Angle  with 
the 
Horizon. 

i 

1:400 

13.2 

0°  8'  36" 

3i 

28^ 

184.8 

2°  0'  16" 

£ 

1:200 

26.4 

0  17  11 

3f 

26§ 

198 

2     8  51 

f 

1:150 

39.6 

0  22  55 

4 

25 

211.2 

1   17  26 

1 

1:100 

52.8 

0  34  23 

4i 

23^ 

224.4 

2  26  10 

H 

1:   80 

66 

0  42  58 

44- 

22^ 

237.6 

2  34  36 

1* 

1:   66f 

79.2 

0  51  28 

4f 

21 

250.8 

2  43  35 

if 

1:    57^ 

92.4 

0  51 

5 

.20 

264 

2  51  44 

2 

1:    50 

105.6 

8     6 

6 

13^ 

316.8 

3  26  12 

2i 

1:   44i 

118.8 

17  39 

7 

14f 

369  .  6 

4     0  15 

2* 

1:   40 

132 

25  57 

8 

1     12^ 

422.4 

4  34  26 

2f 

1:   36* 

145.2 

34  22 

9 

1      111 

475.2 

5     8  31 

3 

1:    33^ 

158.4 

43  08 

10 

1      10 

528 

5  42  37 

3i 

1:    30f 

171.6 

51  42 

CHAPTER  II 
ROAD   AND    PAVEMENT    ECONOMICS 

Good  country  roads  and  city  streets  possess  a  considerable 
value,  as  on  them  depend  largely  the  development  of  the 
financial,  social  and  educational  well-being;  of  the 

«    i  . 

community.     In    cities    and    towns,    smooth    and 

J  good  roads 

comparatively  dustless  roads  are  regarded  as  es- 
sential to  the  comfort  and  health  of  the  inhabitants.  In  the 
rural  districts,  the  conditions  of  life  being  so  different  and 
ways  and  means  entering  so  largely  into  consideration,  the 
same  arguments  do  not  apply,  but  the  monetary  advantages 
of  good  roads  are  none  the  less  apparent. 

No  enumeration  of  the  advantages  of  good  country  roads 
could  include  all  the  benefits,  but  a  few  of  the  most  evident  of 
these  may  be  mentioned,  as  follows: 

1.  Decrease  in  cost  of  haulage. 

2.  Better  facilities  in  the  marketing  of  crops,  thus  permitting 

the  cultivation  of  crops  not  otherwise  marketable — an 
especially  valuable  feature  to  farmers  located  in  the 
vicinity  of  a  large  city. 

3.  The  marketing  of  produce  at  the  most  favorable  times — 

an  important  consideration  in  connection  with  perishable 
products. 

4.  A  wider  choice  of  market. 

5.  The  equalizing  of  railway  traffic  and  mercantile  business 

between  different  seasons  of  the  year. 

6.  The    promotion    of    social    and    intellectual    intercourse 

between  members  of  rural  communities  and  also  be- 
tween rural  and  urban  populations. 

7.  Consolidation  of  rural  schools  and  the  increase  in  their 

economy  and  efficiency. 

8.  Facilitation  of  the  rural  mail  delivery. 

19 


20  THE  ART  OF  ROADMAKING 

9.  Increase  in  value  of  rural  property  by  making  it  more 

accessible  to  cities. 

Highway  improvements  in  rural  districts  should  be   con- 
sidered for  both  their  financial  and  intellectual  benefits,  and 
are  to  be  urged  principally  because  they  increase 
Advantages  ^g  intelligence  and  value  of  the  citizen  to  society, 
city  streets    The  en?ects  of  pavements  on  city  life  are  also  far-- 
reaching  and    important,    but    should    be    studied 
more  particularly  in  connection  with  their  cost,  healthfulness 
and  appearance.     Among  their  principal  advantages  may  be 
mentioned  the  following: 

1.  Decrease  in  cost  of  transportation. 

2.  Increase  in  fire  protection. 

3.  Establishment    of    a    permanent    grade — an    important 

feature   in   connection   with   all   street   improvements. 

4.  Improvement  in  general  appearance  of  streets. 

5.  Improvements    in   standards    of  sanitation  and   health, 

by  decreasing  dust  and  mud  and  facilitating  the  clean- 
ing of  streets. 

6.  Facilitation  of  social  intercourse  and  pleasure   driving. 
These  and  the  many  other  advantages  of  a  well-paved  street, 

naturally  enhance  the  value  of  abutting  property,  so  that  this 
must  also  be  included  in  any  list  of  the  benefits  derived. 

The  chief  financial  advantage  of  good  roads  and  pavements 
is  the  lowering  of  the  cost  of  transportation,  by  permitting 

faster  traveling  and  the  hauling  of  heavier  loads, 
value  of  an<^  by  reducing  the  wear  and  tear  on  horses  and 
road  im-  vehicles.  Just  what  the  economic  value  of  road 
prove-  improvements  may  be  depends  on  location,  cost 

of  improvements,  maintenance  charges,  class  of 
traffic,  and  other  considerations,  and  is  always  a  difficult 
problem  to  solve.  A  distinction  must  be  made  between  traffic 
carried  on  regularly  by  an  organized  transportation  department, 
such  as  an  express  company,  and  occasional  traffic  carried  on 
by  farmers;  also  between  the  transportation  of  perishable 
and  non-perishable  products,  the  marketing  of  the  former 
being  compulsory  under  any  conditions,  while  the  latter  can 
wait  for  comparatively  favorable  conditions. 


ROAD  AND  PAVEMENT  ECONOMICS         21 

The  cost  of  transportation  to  the  average  farmer  producing 
non-perishable  products  depends  chiefly  upon  the  condition 
of  the  road  surface,  and  upon  the  demands  of  general  farm 
work.  Loam  or  clay  roads,  which  form  the  most  common 
variety  in  this  country  are  reasonably  good  when  dry,  while 
sand  roads  are  at  their  worst  when  dry  and  are  therefore  in 
their  worst  condition  during  the  greater  part  of  the  year,  and 
especially  so  during  the  crop  season.  In  a  busy  season,  the 
cost  of  haulage  on  a  fairly  level  loam  or  clay  road  is  probably 
not  over  10  or  12  cents  per  ton-mile,  and  where  farm  work  is  not 
so  pressing,  this  may  be  reduced  to  8  or  10  cents  per  ton-mile.* 

There  is  no  method  of  ascertaining  definitely  the  value  of 
improvements  or  the  saving  in  cost  of  transportation  or  the 
loss  occasioned  by  bad  roads;  the  only  way  of  arriving  at  such 
conclusions  being  either  by  (1)  mere  guess  work;  (2)  a  rough 
estimate  based  upon  the  estimated  annual  saving  per  horse, 
multiplied  by  the  number  of  horses  given  in  the  census  report; 
(3)  statistical  results  published  by  the  United  States  Depart- 
ment of  Agriculture;  (4)  making  an  estimate  of  present  cost 
per  ton-mile  and  an  estimate  of  cost  after  the  improvement. 

While  the  actual  value  can  with  difficulty  be  established,  it 
cannot  be  denied  that  such  improvements  are  beneficial, 

but  before  deciding  upon  their  design,  the  question 

.    A  Ultimate 

of   ultimate   economy   should   be   fully   gone   into.       economy 

This  includes:  of  road 

1.  Interest  on  first  cost.  improve- 

2.  Annual  payments  to   a   sinking  fund  for  the 

extinction  of  the  debt  at  the  end  of  some  time  correspond- 
ing to  the  life  of  the  structure,  or  with  a  fixed  period 
within  which  payment  must  be  made. 

3.  Maintenance  and  cleaning  charges. 

4.  Equal  annual  payments  to  a  depreciation  or  renewal  fund 

which,  properly  invested  for  a  number  of  years  corre- 
sponding with  the  life  of  the  structure,  will  provide  at 
the  end  of  the  term  the  amount  required  for  rebuilding. 

*The  subject  of  "Cost  of  Wagon  Transportation"  was  discussed  very 
fully  by  Prof.  I.  O.  Baker,  in  the  Proc.  of  111.  Soc.  of  Engineers,  vol.  16; 
abstracted  in  Engineering  News,  of  Jan.  31,  1901. 


22  THE  ART  OF  ROADMAKING 

In  the  designing  of  city  pavements  the  questions  of  comfort 
and  luxury  as  affected  by  freedom  from  dust,  noise,  and  slip- 

periness,  enter  very  largely.  Granite,  for  instance, 
affecting8  makes  a  durable  and,  in  the  long  run,  an  economical 
design  of  pavement,  but  its  use  in  cities  is  limited,  if  not 
city  precluded  altogether,  on  the  grounds  that  it  is 

noisy,  slippery,  and  destructive  to  horses'  feet. 
It  will  be  seen,  therefore,  when  attempting  to  adjust  the 
economical  value  of  pavements,  how  local  conditions  and 
necessities  must  be  given  full  weight.  It  may  be  said,  how- 
ever, that  well-paved  sidewalks  and  roadways  form  an  eco- 
nomic and  social  necessity  to  any  community  that  wishes  to 
preserve  its  existence.  Without  them  it  cannot  compete 
with  other  places  thus  properly  equipped.  The  lack  of 
pavements  or  the  presence  of  bad  pavements  impedes  the 
moving  of  people  and  materials,  prevents  proper  street 
cleaning,  endangers  the  comfort  and  health,  and  retards  the 
character,  education,  and  success  of  the  people. 

The  question  of  cost  of  city  pavements  is  a  relative  one,  but 
in  the  matter  of  payment  for  them,  there  is   always  some 

discussion.  The  three  most  common  methods  of 
Methods  of  ..  , 

payment       apportionment  of  cost  are: 

for  city  1.  Muncipality  to  pay  entire  cost. 

2.  Municipality   and   abutting   property   to   pay 

50  per  cent  each. 

3.  Abutting  property  to  pay  entire  cost. 
There  are  arguments  both  for  and  against  each  of  these 
systems.  It  is  claimed  that  (1)  the  residents  who  do  not 
own  a  horse  or  vehicle  or  make  actual  use  of  the  pavement 
should  not  be  required  to  pay  for  it,  ignoring  the  other  ad- 
vantages conferred  upon  them  by  the  pavement;  (2)  as  the 
pavement  is  for  the  benefit  of  the  general  public,  the  cost 
should  be  divided,  which  overlooks  the  distinct  benefits  secured 
by  abutting  property,  but  tends  to  discourage  an  extravagent 
demand  for  improvements;  (3)  the  benefits  accrue  only  to  the 
abutting  property,  which  should,  therefore,  bear  the  entire  ex- 
pense, disregarding  the  fact  that  the  pavement  is  for  the  use  of 
the  general  public  and  benefits  all  the  people  of  the  community. 


ROAD   AND   PAVEMENT  ECONOMICS  23 

In  a  paper  on  "  Theory  and  Practice  of  Special  Assess- 
ments/'* J.  L.  Van  Ornum  gives  a  table  showing  the  apportion- 
ment of  cost  of  pavements  in  fifty  American  cities,  which  shows, 
for  original  paving,  in  11  cases  the  city  pays  all,  in  7  the  cost  is 
divided  and  in  32  the  property  pays  all;  for  re-paving,  in  20 
cases  city  pays  all,  in  8  cost  is  divided  and  in  22  property 
pays  all;  for  grading,  in  16  cases  city  pays  all,  in  6  cost  is 
divided  and  in  28  property  pays  all.  This  table  also  shows 
that  as  a  rule  the  Eastern  and  Southern  cities  pay  a  larger 
proportion  of  the  cost  than  do  the  Western,  which  is  probably 
due  to  the  limited  revenues  of  new  cities  and  to  the  many  de- 
mands upon  the  general  tax  fund.  It  seems  to  be  equitable 
and  just  that  the  cost  should  be  borne  jointly  by  the  private 
property  and  the  city  at  large,  since  then  the  cost  falls  apon 
both  interests  which  directly  profit  by  the  improvement,  and 
neither  receives  a  substantial  benefit  without  sharing  in  its 
cost. 

The  administration  of  highways  is  a  feature  of  road  economics 
that  has  had  much  attention.  Roads  should  not  be  con- 
sidered merely  as  local  facilities  for  traffic;  it  is 

possible   to   develop   them   into   great   trunk   lines  Admmistra- 

u        u        •  -i        i  tlon  °* 

with  many  branches,  just  as  a  railroad  may  have  highways 

many  branches  connecting  the  main  line  with 
fertile  agricultural  districts  and  great  commercial  centers. 
One  of  the  greatest  values  of  the  road  is  in  reaching  where  the 
railroad  cannot.  There  is  no  other  means  of  traveling  or  haul- 
ing which  possesses  the  advantages  of  through  communication 
from  farm  and  garden  to  market,  from  house  to  office,  from 
dairy  to  factory  or  shop,  or  for  pleasure  travel,  that  are  offered 
by  a  complete  and  consistent  system  of  roads. 

The  management  of  roads  in  this  country  rests  almost 
entirely  upon  local  township  or  county  authorities,  and 
this  makes  it  difficult  to  secure  either  good  country  roads 
or  an  efficient  road  administration.  As  a  remedy  it  has 
been  urged  that  roads  be  classified  according  to  their  im- 
portance into  State,  County,  and  Township  roads,  each  class 

*  Trans.  Am.  Soc.  C.  E.,  Vol.  38. 


24  THE  ART  OF  ROADMAKING 

to  be  under  a  corresponding  administrative  board.     Similar 

classifications  are  made  in  many   European  coun- 
r/uropean  .    . 

systems         tries,  and  their  systems  of  administration,   which 

of  man-  have  been  in  force  for  many  years,  have  produced 
agement.  ^  magnificent  rOads  seen  in  Europe  to-day.  In 
France,  where  the  road  system  has  been  brought  to  the  highest 
state  of  efficiency,  there  are  five  great  classifications: 

1.  Routes   Nationales,    or    national    highways,    government 
roads,  managed  by  government  engineers  of  the  Department 
of  Bridges  and  Roads  (Fonts  et  Chaussees) . 

2.  Routes  Departmentales,   or  department  highways,   main- 
tained at  the  joint  cost  of  the  government  and  the  communes. 

3.  Chemins    Vecivaux   de   Grande   Communication,   or   main 
feeder  roads. 

4.  Chemins  Vecivaux  d'lnteret  Commune,  or  district  roads. 
These  two  classes  are  made  at  the  cost  of   the   communal 

funds,  with  departmental  or  government  subsidies,  and  are 
maintained  largely  by  the  Department,  partly  by  the  com- 
munes, and  partly  by  individual  labor. 

5.  Chemins   Vecivaux  Ordinaires,  or  small  local  or  parish 
roads,  made  by  the  communes  with  government  subsidies,  and 
maintained  by  communal  tax  and  a  part  of  the  days  of  "presta- 
tion." 

In  Germany  the  control  of  the  public  roads  belongs  to  the 
several  states,  and  the  standard  of  maintenance  in  some  is 
very  high.  There  are  usually  two  divisions:  the  Staats- 
Strassen,  or  state  roads,  and  the  Lands-Strassen,  or  local 
roads.  In  Italy  and  Spain  there  are  three  classes  of  roads: 
National,  Provincial,  and  Communal.  In  Austria  there  are 
Provincial,  Subventioned  or  Competition,  and  Community 
roads,  under  the  authority  of  provincial  committees,  dis- 
trict road  boards  and  the  communities.  In  Denmark  there 
are  four  classes  of  roads,  classed  according  to  the  number  of 
vehicles  that  pass  over  them. 

In  the  United  States  the  most  important  highway  undertak- 
ing is  that  of  the  Massachusetts   State  Highway 
Commission,  appointed  in  1893  by  an  Act  of  the 
Legislature  for  improving,  making,  and  encouraging 
the  making  of  roads.     In  several  other  states  there  are  high- 


ROAD  AND  PAVEMENT  ECONOMICS         25 

way  departments,  or  commissioners,  some  of  which  are  em- 
powered to  give  financial  and  other  help  for  country  and 
local  roads.  But  neither  a  general  system  of  road  classifica- 
tion nor  of  state  aid  for  road  building  and  maintenance  has 
as  yet  been  established. 

For  the  maintenance  of  country  roads  there  are  three  forms 
of  tax: 

1.  A  tax  upon  the  traveler,  by  a  system  of  toll  roads,  con- 
ducted on  the  theory  that  the  travelers  over  a  road  are  the 
recipients  of  its  benefits  and  should  pay  for  it.     The  disad- 
vantages and  the  many  evils  of  this  system  have  caused  it  to 
be  almost  entirely  abolished  both  in  Europe  and  in  the  United 
States. 

2.  A  capitation  tax,  or  poll-tax,  which  is  levied  in  nearly 
all  states.     This  is  usually  paid  in  labor  and  in  many  parts 
of  the  country  is  nearly  the  sole  support  of  the  roads. 

3.  A  property  tax,  either  by  a  special  assessment  on  all 
property  within  a  certain  distance  of  the  improvement,  or  by  a 
general  tax  on  all  property  within  stated  districts. 

The  labor  tax  system,  as  regularly  employed  in  many  states, 
was  brought  from  England,  and  is  a  survival  of  the  feudal 
method  of  requiring  all  able-bodied  men  to  render 
public  service.     It  is  still  in  operation  in  some  of      ta^ 
the  European  countries,  but  upon  a  much  less  ex- 
tensive scale  than  in  this  country.     The  system  has  many 
defects,   but  these  are  owing  rather  to  poor  administration 
than  to  the  actual  working  of  the  system,  and  may  be  classified 
as  follows: 

1.  Indifferent  and  inefficient  work. 

2.  Impossibility  of  getting  the  work  done  at  the  mo&t  suit- 
able times. 

3.  No  selection  of  the  laborer. 

All  of  these  are  important  considerations,  but  they  are  partly 
counterbalanced  by  the  facts:  (1)  that  the  farmer  is  willing 
to  pay  more  in  labor  than  in  money;  (2)  that  in  rural  districts 
it  is  impossible  to  secure  anyone  to  do  road  work  at  reasonable 
wages  at  the  most  suitable  times,  and  (3)  that  if  the  tax  were 
paid  in  money  there  would  be  no  certainty  that  the  labor 


26  THE  ART  OF  ROADMAKING 

would  be  any  more  efficient.  The  labor-tax  system  is  not 
necessarily  the  cause  of  inferior  roads  nor  the  cash-tax  in  itself 
the  cause  of  improved  roads.  The  one  thing  necessary  for 
successful  road  management  is  effective  supervision  of  the 
work.  Without  it  neither  system  will  accomplish  much,  and 
with  it  either  system  will  do  well. 

The  methods  of  payment  for  the  maintenance  cf  city  pave- 
ments have  already  been  briefly  mentioned;*  the  system  of 

maintenance   is   usually   either   by   a    contractor's 
Mamten-  .   . 

ance  of         guaranteef  for  a  specified  time,  or  by  the  munici- 

city  pave-      pality,  depending  upon  local  conditions. 

In  the  course  of  an  address  before  the  Civic 
Association  of  Morristown,  N.  J.,  in  1908,  Col.  J.  W.  Howard 
spoke  of  the  difficulties  experienced  by  municipalities  in  the 
methods  of  pavement  construction  and  maintenance,  and 
said: 

"  The  best  pavements  are  obtained  and  maintained  by 
employing  experienced,  efficient  and  honest  men  and  by  elimi- 
nating so-called  practical  politicians,  whether  office  holders, 
party  managers  or  others.  Paving  contractors  and  the  men 
who  supply  paving  materials  not  only  must  include  in  their 
charges  against  a  city  or  taxpayer  the  cost  of  construction  or 
materials  and  labor,  but  also  any  amounts  they  expend  for 
bribery  (called  " graft"  by  many),  and  political  contributions, 
thus  either  increasing  the  cost  of  pavements  or  making  their 
quality  bad.  If  full  printed  forms  of  contracts  and  complete 
specifications  are  prepared  by  a  competent  paving  expert  not 
under  local  influences,  the  community  receives  the  benefit  of 
the  experience  of  many  other  places,  and  if  the  specifications 
enumerate  the  preliminary  laboratory  tests  which  the  paving 
materials  must  meet,  and  fully  describe  the  materials,  methods, 
and  processes^  then  with  honest  inspection,  good  and  durable 
pavements  will  be  the  result." 

A  serious  cause  of  the  destruction  of  pavements  in  the 
United  States  and  a  difficulty  in  the  way  of  proper  maintenance, 

*  The  subject  of  the  apportionment  of  expenses  and  the  system  em- 
ployed in  building,  maintaining,  and  grading  roads  and  pavements  is 
an  important  one  and  is  discussed  very  fully  in  Baker's  "Roads  and 
Pavements"  and  in  Byrne's  "Highway  Construction." 

fThe  subject  of  "Guarantees"  is  discussed  briefly  in   Appendix  II, 


ROAD  AND  PAVEMENT  ECONOMICS  27 

is  the  frequency  with  which  they  are  torn  up  for  the  intro- 
duction and  replacing  of  underground  pipes.  As 
the  pavement  should  be  impervious  to  water,  it  °PenmS  °* 
should  also  be  impervious  to  the  destroying  pick  ments. 
and  shovel  of  the  ignorant  wrorkman,  to  whom  this 
work  is  usually  assigned.  A  pavement  once  torn  up  in  this 
way  is  never  properly  repaired,  and  will  always  be  a  source  of 
expense.  In  most  European  countries,  neither  corporations 
nor  individuals  are  permitted  to  disurb  the  pavements,  all 
removals  and  restorations  being  done  by  the  city's  own  em- 
ployees, upon  the  deposit,  by  the  parties  who  required  the  open- 
ing of  the  street,  of  a  sufficient  sum  to  cover  the  expense  of  each 
piece  of  paving  done,  at  a  fixed  price  per  yard,  according  to 
the  kind  of  pavement.  The  only  way  to  entirely  avoid  this 
disturbance  is  by  the  introduction  of  a  series  of  subways  under 
the  pavements  for  wires,  pipes,  etc.;  a  costly,  but,  in  the  end, 
an  economical  remedy. 


CHAPTER     III 

PRINCIPLES    UNDERLYING    THE    SELECTION    OF 
PAVEMENTS  FOR   DIFFERENT   PURPOSES 

A  ROAD  may  be  defined  as  a  highway  or  thoroughfare  for 
the  use  of  foot  travelers  or  vehicles;  a  PAVEMENT  (from  the 

Latin  Pavimentum,  "a  floor  rammed  or  beaten 
Road  and  down")  as  the  artificial  surface  or  covering  of  the 
definitions"  road-  It-8  purpose  is  not,  as  may  be  commonly 

supposed,  to  support  the  vehicles  passing  over  it, 
the  weight  of  which,  together  with  that  of  the  covering  itself, 
must  be  actually  borne  by  the  natural  soil,  but  it  is  (1)  to 
distribute  the  pressure  of  the  traffic  over  a  sufficient  area  of 
sub-soil ;  (2)  to  facilitate  travel  by  reducing  the  resistance  to 
traction  to  the  lowest  practicable  limit,  at  the  least  cost  for 
construction  and  maintenance,  and  (3)  to  secure  a  water- 
tight covering  that  will  preserve  the  natural  soil  from  the 
effects  of  moisture. 

Require-  ^ne  Pavemem%  or  road  covering,  is  composed  of 

ments  of  a    suitable  materials  laid  upon  a  firm  bed,  or  upon  an 
good  pave-    artificial  foundation  from  which  water  is  excluded 

by  suitable  drainage,  and  should  be: 

1.  Cheap — that  is,  low  as  to  first  cost. 

2.  Hard  and  durable,  to  resist  wear  and  disintegration. 

3.  Easily  cleaned. 

4.  Adaptable  to  every  grade  with  little  resistance  to  traction. 

5.  Non-slippery,  affording  a  good  foothold  for  horses. 

6.  Cheaply  maintained. 

7.  Suitable  for  every  class  of  traffic. 

8.  Impervious  to  water,  yielding  neither  dust  nor  mud,  and 
noiseless. 

Of  these  requirements  (1),  (2)  and  (6)  affect  the  taxpayers, 
both  as  to  the  serviceable  life  of  the  pavement  and  as  to  the 

28 


PAVEMENTS  FOR  DIFFERENT  PURPOSES  29 

amount  of  annual  repairs;  (3)  and  (8)  affect  the  occupiers  of 
adjacent  premises,  who  suffer  physically,  and  the  owners  of 
the  premises,  whose  income  from  rents  is  diminished  by  these 
disadvantages;  (4),  (5)  and  (7)  affect  the  traffic  and  determine 
the  cost  of  haulage  and  limitations  o£  loads,  speed,  wear  and 
tear  of  horses  and  vehicles. 

Assuming  an   ideal    pavement    possessing    these    different 
properties  in  perfection,  and  giving  it  a  value  of 
100,  Tillson*  assigns  to  each  its  proportional  value  Of  an 


of  the  whole  as  follows:  pavement 

Cheapness  .................  14 

Durability  .................  21 

Ease  of  cleaning  ............  15 

Light  resistance  to  traffic.  ...  15 

Non-slipperiness  ............  7 

Ease  of  maintenance  ........  10 

Favorableness  to  travel  ......  5 

Sanitariness  ................  13 

100 

Baker  t  divides  the  properties  of  the  ideal  pavement  into 
Economic  and  Sanitary  Qualities  and  Acceptability,  and  gives 
a  table  showing  the  following  relative  values  of  the  different 
qualities  : 

Economic  Qualities: 

Low  first  cost  ....................      15 

Low  cost  of  maintenance  ..........     20 

Ease  of  traction  ..................      10 

Good  foothold  ....................       5 

Ease  of  cleaning  .................      10 

60 

Sanitary  Qualities: 

Noiselessness  ....................     15 

Healthfulness  ..........  :  .........      10 

—     25 

*  "Street  Pavements  and  Paving  Materials,"  p.  147. 
f  "Roads  and  Pavements,"  p.  583. 


30  THE  ART  OF  ROADMAKING 

Acceptability : 

Freedom  from  dust  and  mud 10 

Comfortable  to  use 3 

Non-absorbent  of  heat 2 

15     100 

Cheapness  is  placed  first  as  the  first  cost  of  a  material  is  a 
question  of  vital  importance  in  deciding  upon  its  availability. 
No  matter  how  desirable  or  how  economical  a  material  may 
be,  if  the  property  owners  cannot  pay  for  it,  the  question  is 
settled  at  once  and  a  committee's  recommendation  is  often 
rejected  when  its  wisdom  is  not  questioned,  simply  on  this 
account. 

Durability  is  also  an  economic  question,  upon  which  de- 
pends ultimate  cost,  and  it  must,  therefore,  be  considered  in 
connection  with  first  cost.  A  pavement  may  be  cheap,  and 
also  fill  several  other  requirements  but  it  cannot  be  a  complete 
success  unless  it  has  durability.  This  is  affected  by  many  and 
various  conditions  and  is  measured  by  the  amount  of  traffic 
tonnage  it  will  bear  before  it  becomes  so  worn  that  the  cost 
of  replacing  it  is  less  than  the  expense  incurred  by  its  use. 

Ease  of  Cleaning.  The  experience  of  many  cities  has  demon- 
strated the  importance  of  this  quality.  Street  cleaning  is 
an  expensive  process  and  considerable  attention  is  given  to 
devices  and  systems  of  construction  that  will  effect  economies 
in  this  direction. 

Resistance  to  Traction  is  an  important  item,  as  one  of  the 
objects  in  the  building  of  a  pavement  is  to  effect  its  greatest 
possible  reduction. 

Non-slipperiness  is  necessary  in  a  pavement,  as  on  it  de- 
pends the  efficiency  of  a  draft  horse  or  other  motive  power. 

Ease  of  Maintenance  is  closely  allied  to  first  cost.  There 
is  not  a  pavement,  just  as  there  is  no  other  work  of  man, 
however  perfect  originally,  that  will  not  require  constant  at- 
tention to  keep  it  in  its  original  condition,  and  the  construc- 
tion that  requires  the  least  attention  to  keep  in  good  repair, 
and  allows  that  to  be  done  at  the  least  expense,  is  the  best. 

Suitability  for  Traffic  means  the  ease  and  comfort  obtained 


PAVEMENTS  FOR  DIFFERENT  PURPOSES 


31 


by  the  user  of  the  road  and  the  wear  and  tear  on  the  horses 
and  vehicles  used. 

Sanitariness.  To  be  sanitary  a  pavement  must  be  im- 
pervious to  water  in  order  to  prevent  the  accumulation  of 
decaying  organic  matter,  garbage,  droppings,  and  various 
kinds  of  filth  from  collecting  in  joints  or  soaking  through  the 
surface  to  the  underlying  soil,  out  of  reach  of  the  street  cleaners. 
It  should  be  of  material  that  will  not  decay,  or  otherwise 

yield  dust  or  mud.     Under  this  head  should  also 

,  .  ,  .  ,.  Relative 

be    classed    noise,    which    is    an   important    factor    vaiues  Of 

affecting  the  comfort  of  the  persons  living  adjacent    qualities  of 
to  or  otherwise  using  the  street.  different 

Tillson*    makes    a    comparison    of    the    various 
pavements  in  connection  with  these  properties,  as  shown  in 
the  accompanying  table : 

TABLE  III 

SHOWING  HOW  EACH  MATERIAL  STANDS  RELATIVELY  TO 
OTHERS  AND  ALSO  WHAT  PROPORTION  OF  THE  PROP- 
ERTIES OF  A  PERFECT  PAVEMENT  IS  POSSESSED  BY 
EACH  PAVEMENT  UNDER  CONSIDERATION 


Pavement  Qualities. 

Percentage. 

Granite  A. 

Granite  B. 

Asphalt. 

M 

o 

*n 

PQ 

Belgian. 

1 

Cobblestone. 

Cheapness  . 

14 

9 

4 

4 

3 

5 

7 

14 

Durability  

?1 

21 

17 

15 

13 

17 

7 

15 

Ease  of  cleaning  .  . 

15 

11 

8 

15 

1? 

7 

5 

?, 

Light  resistance  to  traffic  
Non-slipperiness 

15 
7 

7 
6 

6 

5 

15 
3 

12 
6 

6 
3 

6 

7 

4 

5 

Ease  of  maintenance  
Favorableness  to  travel  
Sanitariness  

10 
5 
18 

10 
3 
q 

7 
2 
7 

6 
5 
13 

6 
4 
11 

7 
2 
5 

3 
5 
5 

2 
0 

?, 

Total  

100 

69 

56 

76 

67 

52 

45 

44 

Making  Asphalt  the  standard  at  100,  the  values  of  the  others 
will  be:  Granite  A,  91;  Brick,  88;  Granite  B,  74;  Belgian,  68; 
Macadam,  59;  Cobblestone,  58. 


*  "Street  Pavements  and/Paving  Materials,"  p.  167. 


32 


THE  ART  OF  ROADMAKING 


The  United  States  Forestry  Service  recently  made  an 
investigation  in  order  to  obtain  opinions  from  engineers  of 
a  number  of  American  cities  who  have  had  experience  with 
the  modern  creosoted  wood  block  pavement  as  to  the  com- 
parative qualities  of  different  kinds  of  pavements.  This 
was  made  in  a  form  slightly  modified  from  the  one  presented 
above,  by  Tillson,  and  resulted  in  the  percentages  given  in 
Table  IV,  in  which  the  figures  given  are  the  averages  of  ten 
replies  to  the  inquiry.  In  this  table  the  pavement  ranking  first 
under  any  given  quality  is  given  the  full  quality  percentage, 
the  rest  grading  down  from  this  value  in  proper  proportion. 

TABLE  IV 
COMPARATIVE   VALUE    OF   DIFFERENT   PAVEMENTS* 


Pavement  Qualities. 

•mage. 

p 

• 

,1 

^2 

a 

a 

li 

o 

1 

-^53 

~  pQ 

'o 

u 

OK* 

o 

9 

Vl^~' 

CO  ^ 

*Jj 

c3 

2n  ^ 

& 

0 

CQ 

•< 

B 

s 

o 

f   Cheapness  (first  cost)  . 

14 

4.0 

4.0 

6.5 

6.5 

7.0 

14.0 

4.5 

Durability  

20 

20.0 

17.5 

10.0 

14.0 

12.5 

6.0 

14.0 

Ease  of  maintenance.  . 

10 

9.5 

10.0 

7.5 

8.0 

8.5 

4.5 

9.5 

Ease  of  cleaning  

14 

10.0 

11.0 

14.0 

14.0 

12.5 

6.0 

14.0 

Low  tractive  resistance 

14 

8.5 

9.5 

14.0 

13.5 

12.5 

8.0 

14.0 

5'Non-slipperiness  

7 

5.5 

7.0 

3.5 

4.5 

5.5 

6.5 

4.0 

Favorableness  to  travel 

4 

2.5 

3.5 

4.0 

3.5 

3.0 

3.0 

3.5 

[Acceptability  

4 

2.0 

2.5 

3.5 

3.5 

2.5 

2.5 

4.0 

y   Sanitary  quality  

13 

9.0 

8.5 

13.0 

12.0 

10.5 

4.5 

12.5 

Total  

100 

71.0 

73.5 

76.0 

79.5 

74.5 

55.0 

80.0 

Average  cost  per  square 

yard  (1905) 

$3.26 

$3.50 

$2.36 

$2.29 

$2.06 

$0.99 

$3.10 

Acceptability  includes  noise,  reflection  of  light,  radiation  of  heat,  emission  of  un- 
pleasant odors,  etc.,  and  chiefly  concerns  the  pedestrian  and  the  adjoining  resident. 

Cost  per  square  yard  includes  concrete,  but  not  excavation,  curbing,  etc. ;  except  for 
macadam  which  is  not  usually  laid  on  concrete. 

As  in  Table  III,  giving  Asphalt  (sheet)  the  value  of  100, 
the  values  of  the  others  will  be,  approximately:  Granite, 
95.0;  Sandstone,  98.;  Asphalt  (block),  104;  Brick,  99;  Mac- 
adam, 72;  Creosoted  wood,  104. 

*  From  Circular  141,  Forest  Service,  U.  S.  Department  of  Agriculture. 


PAVEMENTS  FOR  DIFFERENT  PURPOSES 


33 


Use  of 
tables  in 
selection 
of  pave- 
ments. 


By  a  proper  understanding  and  use  of  these  tables,  the  prin- 
ciples used  in  their  construction  can  be  easily  applied  to  any 
particular  case.  One  or  two  examples  will  suffice 
to  make  this  clear.  Assume  a  street  over  which 
the  traffic  must  be  heavy  and  continuous;  ulti- 
mate cost  is  of  so  great  importance  that  it  over- 
rules first  cost.  Light  resistance  to  traffic  and 
foothold  for  horses  are  ruling  elements,  so  that  a  given  power 
may  move  its  maximum  load.  The  items  first  to  be  studied 
are,  then:  durability,  maintenance,  traction,  and  non-slipper- 
iness.  Consulting  Table  IV  and  combining  the  values  for 
these  items,  Granite  has  a  value  of  43.5;  Sandstone,  44.0; 
Asphalt  (sheet),  35;  Asphalt  (block),  40;  Brick,  39;  Mac- 
adam, 25,  and  Creosoted  wood,  41.5.  Granite  and  sandstone 
have  almost  equal  advantages  and  a  selection  must  be  made 
between  them,  according  to  local  conditions. 

In  a  residence  district  built  up  with  homes,  there  is  quite 
a  different  problem.  Cost,  durability,  and  maintenance  are 
secondary  considerations.  Ease  of  cleanliness,  non-slipperiness, 
favorableness  to  travel,  acceptability,  and  sanitariness  are  the 
governing  characteristics,  and  we  find  that  Granite  has  a  value 
of  29;  Sandstone,  32;  Asphalt  (sheet),  38;  Asphalt  (block), 
37.5;  Brick,  34;  Macadam,  22.5,  and  Creosoted  wood,  38. 
Asphalt  or  creosoted  wood,  either  of  which  possesses  all  the 
desirable  qualities  in  so  high  a  degree,  should  be  selected 
without  question. 

The  following  table  shows  the  comparative  rank  of  pave- 
ments in  the  order  of  their  merit,  as  given  by  Byrne:  * 

TABLE  V 

COMPARATIVE  RANK  OF  PAVEMENTS,  NAMED  IN  THE 
ORDER  OF  THEIR  MERIT 


Durability. 

Service- 
ability. 

Hygienic 
fitness. 

Service  on 
Grades. 

Gross  An- 
nual Cost. 

Facility  for 
Cleansing. 

1 

2 
3 

Granite 
Asphalt 
Brick 

Asphalt 
Brick 
Wood 

Asphalt 
Brick 
Granite 

Granite 
Brick 
Wood 

Asphalt 
Brick 
Wood 

Asphalt 
Brick 
Granite 

4 

Wood 

Granite 

Wood 

Asphalt 

Granite 

Wood 

*  "Highway  Construction,"  p.  21. 


34  THE  ART  OF  ROADMAKING 

In  general,  the  selection  of  a  suitable  pavement  to  meet  any 
local  conditions  of  traffic  is  a  problem  involving  questions  of 
adaptability,  desirability,  serviceability,  durability,  and   cost; 
but,    apart    from    strictly    local    considerations,    appearance, 
cleanliness,  healthfulness,  and  noise  should  be  con- 
sidered. 

In  regard   to    adaptability,   the    materials   most 
commonly  employed  are: 

1.  For  country  roads — earth,  sand,  clay,  gravel,  and  broken 

stone. 

2.  For   suburban   streets,   parks   and   pleasure   drives,   and 

main  country  roads — broken  stone  (macadam),  tar- 
macadam,  gravel,  vitrified  brick. 

3.  For   city   streets   having   heavy    and    constant   traffic — 

rectangular  blocks  of  stone  laid  upon  a  concrete  founda- 
tion with  the  joints  filled  with  bituminous  or  Portland 
cement  grout. 

4.  For   city   streets   devoted  to  lighter   traffic,   and   where 

comparative  noiselessness  is  essential — sheet  asphalt, 
asphalt  block,  vitrified  brick,  creosoted  wood  block, 
concrete. 

The   desirability    of   any   pavement    depends    partly    upon 
its    fitness    for  service,  but   is  dependent  principally  on  the 

personal  prejudices  of  the  persons  using;  or  seeing 
Desirability.    :.  V1        . 

it.      Between    two    or    more    pavements  alike    in 

cost  and  durability,  there  will  always  be  a  diversity  of 
opinion  as  to  desirability  according  as  each  possesses  qualities 
that  make  it  satisfactory  for  the  individual  purposes  of 
each  person.  The  economic  desirability  is  governed  by  the 
ease  of  movement  over  a  pavement,  and  is  measured  by 
the  tractive  power  required  to  move  a  given  weight  over 
it. 

The  serviceability  of  a  pavement  is  its  quality  of  fitness  for 

Serviceabilit     Use>  as   measurec^   ^J  tne   expense   caused  to   the 
traffic   using  it,   such    as  the   wear  and    tear  on 
horses,  vehicles,  loss  of  time,  etc.     This  is  estimated  to  be  as 
follows : 


PAVEMENTS   FOR  DIFFERENT  PURPOSES  35 

Cents  per  Mile  Traveled. 

On  Cobblestones 5 

Belgian  block 4 

Granite  block 3 

Wood 2.5 

Broken  stone  in  first-class  condition 1.2 

Asphalt 1 

Serviceability  also  largely  depends  on  the  amount  of  foot- 
hold it  offers  to  horses,  provided,  however,  that  the  surface 
friction  does  not  absorb  too  large  a  percentage  of  the  tractive 
force  required  to  move  a  given  load  over  it.  Cobblestones 
afford  an  excellent  foothold,  and  for  that  reason  were  largely 
employed  between  the  tracks  of  the  early  stone-track  roads, 
and  later  by  horse-car  companies  for  paving  between  the  rails. 
The  resistance  of  their  surface  to  motion,  however,  requires 
the  expenditure  of  about  280  pounds  tractive  force  to  move 
a  load  of  one  ton,  which  makes  it  unserviceable  for  many 
purposes,  as  compared  with  asphalt,  which  affords  the  least 
foothold,  but  requires  a  tractive  force  of  only 

about  30  pounds  per  ton  to  overcome  the  resist-  ComParative 

"  .  safety  of 

ance  it  offers  to  motion.  pavements. 

The   materials  affording  the    best    foothold    for 
horses,  are  stated  as  follows  in  the  order  of  their  merit.* 

1.  Earth,  dry  and  compact. 

2.  Gravel. 

3.  Broken  stone  (macadam). 

4.  Wood. 

5.  Sandstone  and  brick. 

6.  Asphalt. 

7.  Granite  blocks. 

Observations  on  the  comparative  safety  of  different  pave- 
ments show  that : 

1.  Asphalt  is  most  slippery  when  merely  damp,  and  safest 
when  perfectly  dry. 

2.  Granite  is  most  slippery  when  dry  and  safest  when  wet. 

*  Byrne:  "Highway  Construction,"  p.  7. 


36  THE  ART  OF  ROADMAKING 

3.  Wood  is  most  slippery  when  damp  and  safest  when 
dry. 

Granite  is,  therefore,  least  safe  and  wood  and  asphalt  most 
safe  when  clean.  Slipperiness  can  be  prevented  by  the  sprink- 
ling of  sand  on  asphalt,  and  gravel  on  wood,  but  both  make 
dirt.  While  the  sand  tends  to  wear  and  damage  to  the  asphalt, 
the  gravel  tends  to  the  preservation  of  the  wood. 

The  durability  or  life  of  the  different  pavements 
Durability.     ig  given  ag. 

Granite  block 12  to  30  years 

Sandstone 6  to  12  years 

Asphalt 10  to  14  years 

Wood 3  to    7  years 

Limestone 1  to    3  years 

Brick 5  to  ?  years 

Macadam ?  years 

Cost  is  always  an  important  question,  and  while  cheapness 
is  placed  as  the  first  requirement  of  an  ideal  pavement  it  must 
be  considered  in  connection  with  the  returns  on  the 
investment.     The  most  expensive  pavement  is  not 
always  the  best,  nor  is  the  cheapest  the  most   economical. 
The  most  economical  is  the  one  which  gives  the  most  profitable 
returns  in  proportion  to  the  expenses  incurred  in  its   con- 
struction and  maintenance. 

" Cheapness''  in  road-building,  as  in  nearly  every  other  mat- 
ter, may  be  false  economy.  If  the  first  cost  is  to  be  charged 
against  the  abutting  property,  the  average  property  owner 
will  look  for  cheapness  without  realizing  the  early  destruction 
of  the  pavement  and  the  annoyance  and  expense  of  endless 
repairs.  A  good  pavement  costs  more  than  a  poor  one,  but 
it  is  easier  and  cheaper  to  keep  in  repair,  and  will  last  many 
years  longer,  while  its  other  economic  benefits,  comprising 
greater  and  easier  facilities  for  traveling,  less  cost  for  repair 
to  vehicles,  less  wear  on  horses,  saving  of  time,  and  the  ease 
and  comfort  of  those  using  it,  will  much  more  than  compensate 
for  the  extra  expense  involved  in  building  it. 


PART  II 

COUNTRY,  SUBURBAN,  AND  MISCELLANEOUS 

ROADS 


CHAPTER   IV 
LOCATION   OF   COUNTRY   ROADS 

The  problems  involved  in  the  construction  of  country  roads 
are  quite  different  from  those  connected  with  similar  opera- 
tions on  city  pavements,  and  may  in  general,  be  divided  into 
three  periods: 

1.  Locating,  or  laying  out,  the  route; 

2.  Making  the  roadbed; 

3.  Making  the  road  surface. 

The  location  of  country  roads  is  the  scientific  determination 
of  the  most  suitable  route  and  gradients  for  the  proposed 
line  of  communication.  In  the  earliest  days  or  in  the  early 
days  of  new  settlements,  routes  were  made  according  to  the 
line  of  least  resistance,  and  without  regard  to  any  considera- 
tions other  than  the  easiest  method  of  traveling,  or  of  convey- 
ing goods,  from  one  place  to  another. 

The  Romans,  at  very  great  expense,  built  their  roads  up- 
hill and   down  hill,  through  swamps  and   forests, 
and  over  all  obstacles,  in  perfectly  straight   lines,    straight 
in  the  belief  that  this  was  the  shortest  distance  be-    and  curved 
tween  two  points  and  constituted  the  best  location.    roads- 

Theoretically  they  were  right,  but  practically  they  were  cor- 
rect to  a  very  limited  degree,  for  a  straight  road  over  a  hill  is 
not  necessarily  any  shorter  than  a  curved  road  around  it.  Both 

37 


a.  Before  Improvement. 


b.  In  Process  of  Construction. 


c.  The  Finished  Road. 
FIG.  3.— The  Evolution  of  a  Country  Road. 


38 


LOCATION  OF  COUNTRY  ROADS          39 

are  curved,  one  in  its  vertical  and  the  other  in  its  horizontal 
plane,  and  they  may  be  precisely  the  same  length,  but  the  one 
over  the  hill  is  said  to  be  straight,  only  because  its  vertical 
curvature  is  less  apparent  to  the  eye. 

Of  the  two  roads  of  equal  length,  the  route  over  the  hill 
has  the  disadvantages  of  greater  first  cost,  greater  mainten- 
ance expense,  greater  damage  from  rains  and  other  causes, 
greater  wear  on  horses  and  vehicles  in  the  haulage 
of  goods  over  it,  and  consequently  greater  cost  to 
those  using  it.  But  even  if  the  level,  curved  road  tages  of 
were  much  longer  than  the  straight  and  steep  straight 
one,  the  former  would,  as  a  rule,  be  the  more 
economical  on  account  of  the  ease  of  travel  over  it. 
"  Straightness  "  in  a  country  road  is  frequently  overrated,  and 
efforts  to  obtain  it  involve  in  many  cases  injury  to  the  beauty 
of  the  road  and  of  the  landscape,  with  no  compensating 
economic  advantages. 

Economy  forms  the  true  basis  of  proper  location;    that  is, 
ultimate  economy  in   making  the  route  as  direct      Econom 
and,  subject  to  drainage  requirements,  as  level  as      the  basis 
practicable,  in  achieving    the    best  results  at  the      of  loca- 
least  present  and  future  expense.  on* 

Too  much  "  economy  "  should  not,  however,  be  urged  in  the 
work  of  location.  There  is  an  old  saying:  "  Nothing  pays  like 
first  cost  in  road-building,"  meaning  simply  that  money 
expended  in  intelligent  study  of  the  location  is  the  most 
economical  expenditure  in  the  construction  of  a  road.  The 
importance  of  the  selection  of  the  best  route  cannot  be  too 
strongly  urged,  because  an  error  made  in  this  first  stage  of 
roadmaking  will  cause  a  heavy  expense  for  rectification,  and, 
until  rectified,  imposes  a  perpetual  tax  upon  the  public  for 
maintenance. 

Gillespie  in  his  book  on  roads  (1847)  gives  a  forcible  instance 
of  the  value  of  road  improvement  by  scientific  loca-    Value  of 
tion.     An  old  road  in  Anglesea,  North  Wales,  rose    scientific 
and  fell  between  its  two  extremities,  a  distance  of    road  loca~ 
24  miles,  a  total  perpendicular  amount  of  3540  feet, 
while   a   new   road,   laid  out  by  Telford  between   the  same 


40 


THE  ART  OF  ROADMAKING 


FIG.  4.— Pocket  Compass,  with  folding  sights. 


FIG.  7. — Pedometer. 


FIG.  5. — Aneroid  Barometer. 


FIG.  8. — Odometer. 


FIG.  6.— Hand  Level. 


Instruments  used  in  Location. 


LOCATION  OF  COUNTRY  ROADS          41 

points,  not  only  reduced  the  road  distance  to  22  miles,  but 
also  reduced  the  rise  and  fall  to  only  2257  feet.  Thus,  1283 
feet  of  perpendicular  height  was  done  away  with  which  every 
horse  passing  over  the  road  had  previously  been  obliged  to 
ascend  and  descend  with  its  load. 

The  principles  observed  and  the  methods  employed  in  the 
location  of  a-  road  are  substantially  the  same  as  used  in  the 
location  of  a  railroad.     Hard  and  fast  rules  cannot'     Methods 
be  laid  down,  for  each  road  must  be  designed  for      employed 
the  place  it  is  to  occupy  and  the  service  it  is  to      in  loca- 
render,  and  is  dependent  upon  many  local  conditions, 
as  well  as  upon  the  topographical  features  and  the  nature  and 
extent  of  the  traffic  that  it  may  develop.     The  problem  in- 
volves considerations  of  distance,  grades,  curves,  width,  and 
the  establishment  of  controlling  points,  and  always  presents 
an  opportunity  for  the  exercise  of  the  most  careful  judgment. 

To  obtain  the  requisite  data  regarding  these  points  upon 
which  to  form  his  judgment,  the  engineer  must  study  maps 
of  the  district  and  must  make  a  personal  reconnoissance,  or 
examination,  of  the  tract  to  be  traversed,  by  either  riding  or 
walking  over  it,  and  carefully  noting  its  principal  physical 
contours  and  natural,  features,  the  immediate  object  being  to 
select  one  or  more  trial  lines,  from  which  the  final  route  may 
be  ultimately  determined. 

In  making  this  reconnoissance,  a  knowledge  of  physical 
geography  is  essential.  Among  the  characteristics  of  the 
country  noted  are:  Character- 

1.  Inclinations  of  the  strata  and  their  nature  and    istics  of 

conditions  as  to  dryness.  country 

2.  Extent  to  which  the  surface  of  the  road  will 

be  exposed  to  the  action  of  the  air  and  the  rays  of  the 
sun. 

3.  Location  of  crossings  of  valleys,  rivers,  and  passes. 

4.  Condition  of  river  beds,   with  a  view  to  secure  stable 

foundations  for  bridges,  etc. 

5.  Sources,  accesses,  and  distances  of  the  supply  of  material 

for  structural  works,  such  as  retaining  walls,  etc.,  and 
for  stones  suitable  for  road  covering. 


42 


THE  ART  OF  ROADMAKING 


FIG.  9.— Contour  Lines. 


LOCATION  OF  COUNTRY  ROADS  43 

6.  Levels  of  all  existing   lines  of   communication,  such  as 

railways,  roads,  canals,  and  of  rivers  and  streams. 
The  instruments  used  in  the  reconnoissance  are: 

1.  Compass,  for  ascertaining  the  direction. 

2.  Aneroid    Barometer,    for   fixing   approximate 

elevation  of  summits. 

3.  Hand-level,  for  measuring  slopes. 

4.  Odometer,  or  Pedometer,  to  determine  the  distance,  the 

former  for  use  with  a  vehicle  and  the  latter  for  use  in 
walking,  but  if  these  instruments  cannot  be  used,  the 
distance  can  be  approximated  closely  enough  for  pre- 
liminary work  by  various  other  means. 
The  irregularities  of  the  surface  of  the  ground  are  laid  out  on 
paper  by  means  of  " contour  lines" — fine  lines  traced  through 
the  points  of  equal  level  over  the  surface  surveyed, 
denoting  that  the  level  of  the  ground  throughout 
the  whole  of  their  course  is  identical;  that  is  to  say, 
that  each  part  of  the  ground  over  which  the  line  passes  is  at 
a  certain  height  above  a  known  fixed  point,  this  height  being 
indicated  by  the  figures  written  against  the  line.     These  lines, 
by   their  greater   or  less   distance    apart,  have  the  effect  of 
shading,  and  make  apparent  to  the  eye,  the  undulations  and 
irregularities  in  the  surface  of  the  country. 

A  map  is  then  made  showing  the  topography  of  the  district 
—the  length  and  directions  of  the  proposed  line;  the  rivers, 
watercourses,  roads  and  railroads;  town,  county  and 
property  boundary  lines,  arid  any  other  matters  of 
interest.  The  nature  of  the  soil;  character  of 
excavations;  width,  depth  and  velocity  of  rivers;  character 
of  banks  and  bottom,  and  other  features  and  figures  that 
cannot  be  shown  on  a  map  or  profile,  are  given  in  an  accom- 
panying "  memoir." 

Levels  are  taken  along  different  lines,  at  regular  intervals, 
and  heights  of  all  objects  that  may  affect  location    Levels  and 
are  noted,    and  "  bench-marks "*  are   established,    bench 
From  these  levels,  a  profile,  or  longitudinal  section    marks- 

*  Reference  marks  made  on  fixed  objects,  such  as  gate  posts,  houses, 
trees,  etc. 


\ 


FIG.  10. — Topographical  Map. 


44 


LOCATION  OF  COUNTRY  ROADS  45 

of  the  proposed  route  is  made,  on  such  a  scale  that  it  will 
show  with  distinctness  the  inequalities  of  the  ground. 

In  regard  to  the  saving  of  distance,  the  value  is  quite  evi- 
dent where  the  road  is  so  situated  that  it  would  enable  teams 
to  make  an  additional  trip  per  day  in  the  hauling 
of  freight.    But  where  the  traffic  is  of  a  more  in-    Val^e  °f 
definite  nature,  or  the  saving  proposed  is  insufficient    tance. 
to    admit  of  additional   trips,   this   value   depends 
upon  the  value  to  other  work  of  the  small  portion  of  time  of 
men  and  teams  which  may  be  saved  by  the  shorter  route — a 
value  which  exists,  but  is  difficult  to  estimate. 

There  are  other  points  of  value  in  the  saving  of  distance, 
which  may  be  summed  up  as  follows: 

1.  The  advantage  to  the   community  of  bringing  various 
points    closer    together,    such    as    bringing    two    towns    into 
closer   relations    or    bringing     country    property    nearer     to 
markets. 

2.  Variation  due  to  the  character  of  the  road  surface:    as 
the  cost  of  transportation  is  less  over  a  smooth  than  over  rough 
surface,  the  value  of  reducing  distance  is  also  less  on  the  smooth 
surface. 

3.  Variation  due  to  gradient:    on  a  road  where  the  ruling 
gradients  are  steep  the  value  is  greater  than  upon  one  with 
light  gradients,  because  of  the  greater  number  of  loads  neces- 
sary to  move  traffic. 

4.  The  cost  of  maintenance  of  a  road  may  be  considered, 
like  the  costs  of  transportation,  to  be  directly  proportional  to 
the  length  of  road,  and  a  saving  of  distance  involves  a  saving 
in  cost  of  maintenance. 

There  are  two  kinds  of  grades:    Maximum  and  Minimum. 
The  "  Maximum  Grade  "  is  the  steepest  which  is 
permissable   and   the    "  Minimum   Grade  "  -is   the 
least  allowable  for  good  drainage. 

A  level  road  is  desirable  and  preferable,  but  as  it  can  seldom 
be  obtained,  the  roadbuilder  must  investigate  the  effects  of 
grades  upon  the  cost  of  construction  and  maintenance,  and 
also  determine  the  most  suitable  grade  under  the  special 
conditions. 


46  THE  ART  OF  ROADMAKING 

Where  there  is  a  grade  to  be  overcome,  it  can  be  reduced  by 

(1)  going  around  the  hill;    (2)  zig-zagging  up  the 

Methods  of    slOpe;    (3)  cutting  through  the  hill.     In  the  case  of 

a  ^on£  s^°Pe'  tne  ^rst  or  secon<^  mus^  be  employed, 
but  if  the  grade  is  short,  the  third  method  is  usually 
the  cheapest. 


FIG.  11. — A  poorly  located  road;  by  turning  to  the  right  a  gentle  grade 
could  have  been  secured  and  the  two  bad  hills  avoided. 

The  determination  of  the  proper  maximum,  or  ruling,  grade 
is  important  and  is  governed  by  two  considerations;  one 
Determina-  re^ating  to  the  power  expended  in  ascending,  and 
tion  of  the  other  to  the  acceleration  in  descending,  the 
maximum  incline.  As  an  ascent,  it  concerns  the  draft  of 
heavy  loads;  as  a  descent,  it  mainly  concerns  the 
safety  of  rapid  traveling. 

Men  and  animals  can  ascend  steeper  slopes  than  they  can 
descend.  A  man  walks  slowly  up-hill  and  quickly  down-hill. 
A  horse  does  the  reverse;  the  steeper  the  ascent,  the  faster  he 
attempts  to  travel,  while  in  descending  he  moves  at  a  slow 
trot  which  gradually  subsides  into  a  walk.  Consequently  the 
inclination  which  admits  of  high  speed  in  descending  practically 
controls  the  maximum  grade. 

This  will  depend  upon    (1)  the  class  of    traffic  that    will 


LOCATION  OF  COUNTRY  ROADS          47 

use  it,  whether  fast  or  slow,  heavy  or  light;  (2)  the  character 
of  the  pavement  adopted;  (3)  the  cost  of  construction.  It  is 
evident,  therefore,  that  no  fixed  maximum  gradient  can  be 
adopted  to  suit  all  conditions.  Experience  has  shown  that  for 
fast  and  light  traffic,  the  maximum  should  not  exceed  2  per 
cent,  or  1  in  50;  for  mixed  traffic,  3  per  cent,  or  1  in  30,  may  be 
adopted;  for  slow  traffic,  combined  with  economy,  5  per  cent, 
or  1  in  20,  should  not  be  exceeded. 

For  bicycle  travel  a  2  per  cent  grade  can  be  ascended  with 
comparative  ease  and  descended  with  little  effort.  Heavier 
grades,  up  to  5  per  cent,  can  be  ascended  by  the  average 
bicycle  rider  without  extremely  arduous  effort  and  descended 
without  serious  danger,  but  grades  above  5  per  cent  are  too 
steep  for  ascent  with  comfort  or  descent  with  assured  safety. 

For  pleasure  driving  the  grade,  when  practicable,  should  not 
exceed  4  per  cent.  A  good  horse  with  a  light  carriage  and  two 
persons  will  trot  easily  up  a  4  per  cent  grade  and  as  easily  down 
without  a  brake.  With  a  higher  gradient  the  strain  in  either 
direction  becomes  increasingly  apparent.  For  freight 
traffic  the  maximum  grade  admissible  is  12  per  Most  suit- 
cent  able  maxi" 

mum 

The  maximum  grades  established  by  experience    grades, 
for  various  paving  materials  are  approximately: 


For  stone  blocks All  grades 

' '    wood  and  brick 5    per  cent,  or  1  in  20 

' '    broken  stone 3    per  cent,  or  1  in  30 

' '    asphalt 2£  per  cent,  or  1  in  40. 

The  maximum  adopted  by  the  French  engineers  is  1 
in  20,  while  that  adopted  in  England  by  Telford  was 
1  in  30. 

It  does  not  follow,  however,  that  the  maximum  grade  is  the 
most   advantageous  grade.     To   determine  the   latter,   every 
element  that  affects  the  cost  of  transportation  must 
be  considered.     It  is  dependent   upon  the  amount  Most  ad~ 
of  traffic,  and  the  cost  of  construction  and  main-  gra(je 
tenance  of  the  highway,  and  has   been  found  by 
experiment  to  be  approximately: 


48  THE  ART  OF  ROADMAKING 

For  mountainous  country,  between  1/20  and  1/30 
"   hilly  country,  between  1/30  and  1/40 

"   level  country,  between  1/40  and  1/50. 

The  establishment  of  a  minimum  grade  is  also  necessary, 
as  well  as  economical,  in  cost  of  maintenance.  All  roads 
bli  h  should  be  higher  in  the  center  than  at  the  sides  in 
mint  of  order  to  shed  the  rain  into  the  side  ditches,  but 
minimum  even  on  the  best  roads  longitudinal  ruts  are  liable  to 
grade.  form  from  excessive  use  or  neglect  of  proper  main- 

tenance, and  these  seriously  interfere  with  the  surface  drainage. 
If  the  road  were  perfectly  level,  every  rut  would  hold  water, 
which  would  soon  soak  into  and  damage  the  road,  whereas 
with  even  a  slight  grade,  every  rut  and  wheel  track  becomes 
a  channel  to  carry  off  the  rain  water. 

The  minimum  grade  established  in  England  is  1  in  80,  or 
1|  per  cent;  in  France  it  is  1  in  125,  or  .8  per  cent,  which  may 
be  adopted  as  a  minimum,  and  in  a  flat  country,  the  roads 
should  be  artificially  formed  into  gentle  undulations  approxi- 
mating this  minimum  limit.  In  the  United  States  it  is  1  in 
200,  or  .5  per  cent. 

When  the  profile  has  been  made  a  grade  line  is  drawn  upon 

it  in  such  a  manner  as  to  follow  its  general  slope,  but  to  average 

its    irregular    elevations    and    depressions.     If    the 

Establishing  ratio  between  the  whole  distance  and  the  height  of 

grade.  ^e  ^ne  ^s  ^ess  than  the  maximum  grade  intended 

to  be  used,  this  line  will  be  satisfactory;    but  if  it 

is    steeper,    the    cuttings    or   the     length    of    the    line    will 

have   to   be   increased — preferably    the   latter,   by    means    of 

curves. 

As  regards  curves  in  roads,  no  fixed  rules  can  be  laid  down. 
The  greatest  radius  possible  should  be  employed,  depending 
Curves  upon  the  width  and  location  of  the  roadway  and 
the  character  of  the  traffic,  but  it  should  not  be 
less  than  100  feet  for  a  12-foot  road,  75  feet  for  a  16-foot  road, 
of  66  feet  for  an  18-foot  road.  In  France,  country  roads  of 
20  feet  width  have  a  radius  of  50  feet;  in  Germany,  it  is 
40  feet. 


LOCATION  OF  COUNTRY  ROADS 


49 


When  the  curve  occurs  on  an  ascent,  the  grade  at  that  place 
must  be  diminished  in  order  to  compensate  for  the  additional 
resistance  of  the  curve.  Curves  may  be  built 
circular  or  parabolic,  the  latter  preferable  when 
possible,  and  the  width  of  the  wheelway  should 
be  increased  to  permit  the  swinging  of  teams  and  to  prevent 
accidents. 


a.  Simple  Curve. 


6.  Compound  Curve. 


c.  Reverse  Curve.  d.  Double  Reverse  Curve. 

FIG.  12. — Types  of  Curves. 

Excessive  crookedness  should  be  avoided  on  account  of 
expense  of  construction  and  maintenance  and  of  the  extra 
time  and  labor  necessary  in  traveling  over  the  road.  Partly 
on  these  grounds  and  partly  on  the  grounds  of  its  dangers  and 
its  inconvenience  as  regards  drainage,  etc.,  a  zig-zag  method- 
of  surmounting  a  hill  should  be  avoided. 

The  width  of  a  road  depends  upon  the  amount  and  nature 
of  the  traffic  to  be  accommodated,  and  cannot  be  standardized. 
Wide  roads  are  best  as  they  expose  a  larger  surface 
to  the  drying  action  of  the  sun  and  wind  and  require      roa*dwa  ° 
less  supervision  than  narrow  ones,  but  the  first  cost 
is  greater  and  in  country  districts  they  are  not  necessary.     In 
many  places  a  rordway  just  wide  enough  for  a  single  team 
is  all  that  is   required.      In  cases  of  more    frequently   used 
roads,     the     minimum    width     should    allow    two  teams    to 
pass  with  safety,  but  in   all    cases   the    width    of   land    ap- 
propriated   for    highway   purposes — the    "  right    of    way  "— 


50 


THE  ART  OF  ROADMAKING 


should  be  sufficient  to  provide  for  future  increase  in 
traffic.  On  main  country  highways,  this  width  should 
allow  for  a  double  roadway — a  paved  center  and  a  natural 
earth  road  at  the  side. 

Some  of  the  most  common  widths  of  roadways  and  i-ights 
of  way  are: 

Right  of  way. 
United  States  .          49J  to  66 


England 66 

Holland 38 

France :  National  roads 66 

Departmental  roads  .  40 

Provincial  roads  ....  33 

Neighborhood  roads  .  26 


Roadway. 

16 
20  to  22 

14 

22 

20 

20 

16 


One  of  the  most  important  points  in  location  is  the  selection 
of  suitable  bridge  sites.     These  are  sometimes  restricted  to  a 
certain  point,  but  if  not,  the  best  possible  site  is 
determined  and  the  location  of  the  road  is  made 


Selection  of 
bridge  sites. 


subordinate  to  it. 
must  be  given  to 


In  this  selection  consideration 


FIG.  13. — Showing  three  bridges,  A,  B,  C,  where  if  a  road  were  put  in  as 
shown  by  the  dotted  lines  only  the  bridge  at  A  would  be  needed,  ami 
the  public  convenience  would  be  served  just  as  well  as  with  the 
present  arrangement. 

1.  The  character  of  the  river  bed,  in  order  to  obtain  the  best 
foundation. 

2.  Stability  of  the  river  banks. 

3.  Straightness  or  curvature  of  the  river,  so  that  the  bridge 
may  be  at  right  angles  to  the  stream-flow  and  if  possible,  over 
a  straight  stretch  of  the  stream. 


LOCATION  OF  COUNTRY  ROADS 


51 


Principles  to 
be  observed 


In  making  the  final  selection  cf  a  route,  some  of  the  basic 
principles  to  be  observed  are:* 

1.  To  follow  the  route  which  affords  the  easiest 
grade. 

2.  To    connect  the  places  by   the   shortest   and  in  final 
most  direct  route  commensurate  with  easy  grades.  s< 

3.  To  avoid  all  unnecessary  ascents  and  descents. 

4.  To  give  the  center  line  such  a  position  with  reference  to 
the  natural  surface  of  the  ground  that  the  cost  of  construction 
shall  be  reduced  to  the  smallest  possible  amount. 

5.  To  cross  all  obstacles,  where  structures  are  necessary,  as 
nearly  as  possible  at  right  angles. 

6.  To  cross  ridges  through  the  lowest  pass  which  occurs. 

7.  To  cross  either  under  or  over  railroads  and  to  avoid  grade 
crossings. 

Stakes  are  placed  at  intervals  along  the  route,  indicating 


FIG.  14. — Construction  Profile. 

curves  and  their  tangent  points  and  careful  notes  are  taken 
of  the  location  of  the  stakes,  so  that  they  can  be' 
replaced  if  disturbed.     Levels  and  cross  levels  are    jjJ^J10^* 
;  taken  and  a  construction,  or  working  profile,  is  then    tion 
'drawn,   indicating   all   elevations,  cuttings,  fillings, 
embankments,  bridges  and  other  features  necessary  to  permit 
making  an  estimate  of  the  work. 


*  Byrne:  "Highway  Construction,"  p.  460. 


52 


THE  ART  OF  ROADMAKING 


FIG,  15. — A  Costly  Piece  of  Grading, 


CHAPTER  V 
CONSTRUCTION  AND   PROTECTIVE  WORKS 

UNDER  this  head  may  be  included  such  works  connected 
with  the  construction  of  the  roadbed,  as  earthwork,  founda- 
tions, bridges,  culverts  and  retaining  walls. 

EARTHWORK 

The  term  "Earthwork"  embraces  all  operations  performed 
in  the  making  of  the  excavations  and  embankments  to  pre- 
pare them  for  the  road  covering,   such  as  the  reduction  of 
gradient  upon  steep  inclinations,  by  cutting  and  filling,  and 
the  making  of  better  drainage  by  raising  the  road  across  low 
ground.     In   its   broadest   sense   and   as   generally 
understood,    " earthwork"    includes   work   in    rock    Classifica- 
as  well  as  in  the  looser  materials  of  the  earth's    earthwork 
crust,    and   for   purposes   of   comparison,    may   be 
classified  with  regard  to  the  ease  or  difficulty  with  which  it 
can  be  excavated,  as  follows : 

1.  Earth,    including   loam,    clay,    sand,    and   loose   gravel. 

This    may    be    further    classified    approximately    as: 
a.  Easy  ground,    6.  Average  ground,    c.  Hard  ground. 

2.  Hardpan,  including  cemented  gravel,  slate,  cobbles  and 

small    boulders,    and    other    materials    of    a    compact 
earthy  nature. 

3.  Loose  rock,  including  shale,  decomposed  rock,  boulders 

and  detached  masses  of  rock,  and  other  material  of  a 
rock  nature  that  may  be  loosened  with  a  pick. 

4.  Solid  rock,  including  all  rock  found  in  place  in  ledges 

and  masses,  and  large  boulders  which  can  be  removed 
only  by  blasting. 

53 


54  THE  ART  OF  ROADMAKING 

In  selecting  the  final  location  and  gradient  of  the  road,  the 

engineer  must   take   into   consideration  the   " equalizing"   or 

"  balancing "  of  the  earthwork,  so  that  the  material 

farthwo'rlf  taken  from  a  cuttm§  may>  as  nearl7  as  possible, 
and  consistent  with  the  distance  and  cost  of  haulage, 
be  sufficient  to  form  an  embankment.  This  redistribution  of 
the  earthwork  along  the  line  of  the  road  is  in  many  cases 
essential  to  economy  in  the  cost  of  the  work,  as  a  surplus  of 
cutting  or  filling  involves  either  waste  or  borrowing,  both 
of  which  cause  additional  expense  for  labor  and  land.  If  there 
is  a  surplus  of  cutting,  the  waste  earth  is  disposed  of  in  con- 
venient banks  adjoining  the  work,  termed  "spoil-banks." 
If,  on  the  other  hand,  there  is  an  excess  of  embankment 
requirements  over  the  supply  from  cuttings,  the  deficiency 
is  obtained  either  by  widening  the  excavations  or  from 
an  excavation  termed  a  "borrow-pit,"  made  in  the  vicinity 
of  the  embankment.  Sometimes,  however,  the  location 
of  cuts  and  fills  makes  it  more  economical  to  either  waste 
the  earth  or  to  borrow  it,  than  to  haul  it  any  considerable 
distance. 

When  the  road  lies  along  the  side  of  a  hill,  this  balancing, 
termed  in  this  case,  "transverse  balancing"  is  accomplished 
by  locating  the  center  line  of  the  road  so  that 
^e  cu^mg  from  °ne  gi^e  will  form  the  embankment 
on  the  other,  unless  the  side  slopes  are  very  steep, 
when  it  is  better  to  make  the  road  mostly  in  cuts  on  account 
of  the  difficulty  of  forming  stable  embankments  on  steep 
slopes. 

The  problem  of  balancing  earthwork  is  a  very  important 
one  in  practice,  for  upon  its  mode  of  solution  depends  a  large 
portion  of  the  cost  of  the  work.  The  most  economical  use 
of  the  material  depends  on  the  machinery  used  In  moving  the 
earth;  the  character  of  the  earth;  the  road  over  which  it  is  to 
be  transported;  the  cost  of  labor  and  land,  and  other  conditions, 
all  of  which  must  be  taken  into  consideration  by  the  engineer 
in  deciding  what  is  best  for  each  particular  case. 

In  making  excavations  or  forming  side  slopes,  it  is  necessary 
to  insure  stability  and  prevent  slipping  or  sliding  of  its  parts 


CONSTRUCTION  AND  PROTECTIVE  WORKS  55 

on  each  other  by  giving  proper  consideration  to  the  "  natural 
slope"  of  the  material  used.     This  is  the  slope   assumed  by 
the  face  of  a  mass  of  earth  after  considerable  exposure  to  the 
elements,  at  which  the  earth,  by  friction  alone,  will  have  per- 
fect stability.     The  angle  made  by  this  slope  with 
the   horizontal   is   the   "angle    of    repose,"   or  the  Natural 
"  angle  of  internal  friction."     Loose  earth  will  re-  brnkment?." 
main  in    equilibrium  with    its    face  at  this  slope; 
if  piled  at  a  greater  slope,  cohesion  will  hold  the  face  at  this 
greater  slope  for  a  time,  but  the  earth  will  soon  crumble  and 
slide  down  until  the  angle  of  repose  is  attained.     This  angle 
depends  on  the  nature  of  the  soil,  the  action  of  the  atmosphere 
and  of  internal  moisture,  being  approximately  as  follows: 

Compact  earth 50°  f :  1 

Rubble 45°  1:1 

Clay  (well  drained) 45°  1:1 

Gravel 40°  1J:1 

Shingle 39°  1J:1 

Dry  sand 38°  1J:1 

Vegetable  earth  (Loam) 28°  If :  1 

Wet  sand 22°  2^:1 

Clay  (wet) 16°  3:1 

For  all  practical  purposes  it  may  be  said  that  in  both 
excavation  and  embankment,  earth,  sand  and  gravel  stand 
at  a  slope  of  H:l,  or  33°  41". 

The  natural  and  strongest  form  of  earth  slopes  is  a  concave 
curve,  with  the  flattest  portion  at  the  bottom,  but  this  form 
is  seldom  given  to  the  slopes  in  construction,  as  straight  or' 
convex  forms  save  excavation  by  the  contractor,  and  will 
continue  to  slip  until  the  natural  form  is  attained.  Figs.  16 
and  17  show  the  contours  of  embankment  and  excavation 
which  have  met  with  the  most  general  approval  of  the  engineer- 
ing profession.  While  it  is  not  usual  to  employ  artificial  means 
to  protect  the  surface  from  the  action  of  the  weather,  it  will 
be  an  ultimate  economy  in  keeping  the  roadways  in  order, 
if  the  side-slopes  are  sown  with  grass-seed,  as  the  roots 


56 


THE  ART  OF  ROADMAKING 


of  the  grass  bind  the  earth  together  and  prevent  slipping, 
which  is  usually  caused  by  the  saturation  of  the  earth  with 
water. 

When  the  earth  is  first  thrown  up  by  a  shovel,  without  break- 
ing down  the  clods,  or  artificial  consolidation  of  any  sort,  it- 
occupies  more  space  than  it  did  in  place,  but  after 

Shrinkage  of  ^e'm^  piaced  in  embankment,  it  subsides  or  shrinks, 
earthwork.  .  '  .  . 

until  it  occupies  less  space  than  in  the  pit  from 

which  it  was  taken,  the  amount  of  this  shrinkage  depending 
on  the  method  of  compacting. 

When  it  is  considered  that  the  earth  in  embankment  is  not 
so  hard  and  firm  as  in  its  original  position,  and  that  it  will 
settle  still  further  after  the  embankment  is  finished,  this 


FIG.  16. — Cross-section  for  Embankment. 


FIG.  17. — Cross-section  for  Excavation. 

"shrinkage  of  earthwork"   may  seem  strange,   but  may  be 
accounted  for  by  the  following  facts:* 

1.  The  continued  action  of  frost  has  made  the  soil  in  its 

natural  position  more  or  less  porous. 

2.  Earth  which  has  been  lying  in  situ  for  centuries  becomes 

more  or  less  porous  through  the  slow  solution  of  their 
soluble  constituents  by  percolating  water. 

3.  The  surface  soil  in  rendered  more  or  less  porous  by  the 

penetration    of    vegetable    roots    which    subsequently 
decay. 

*  "  Roads  and  Pavements,"  I.  O.  Baker,  page  91. 


CONSTRUCTION  AND  PROTECTIVE  WORKS  57 

4.  There  is  ordinarily  more  or  less  soil  lost  or  wasted  in 
transporting  it  from  the  excavation  to  the  embankment. 

From  the  many  experiments  made  to  obtain  exact  data 
regarding  this  shrinkage,  the  following  general  rules  or  prin- 
ciples have  been  deduced:  * 

1.  Taking  extreme   cases,  earth  swells  when  first  loosened 
with  a  shovel,  so  that  after  loosening  it  occupies   1J   to   1^ 
times  as  much  space  as  it  did  before  loosening;  in  other  words, 
loose  earth  is  14  per  cent  to  50  per  cent  more  bulky  than  nat- 
ural bank  earth. 

2.  As  an  average  we  may  say  that  clean  sand  and  gravel 
swell  1,  or  14  to  15  per  cent;  loam,  loamy  sand  or  gravel  swell 
£,  or  20  per  cent;    dense  clay,  dense   mixtures  of   gravel  and 
clay  swell  £  to  |,  or  33  to  50  per  cent,  ordinarily  about  35 
per  cent,  while  unusually  dense  gravel  and  clay  banks  swell 
50  per  cent. 

3.  That  this  loose  earth  is  compacted  by    several    means; 
(a)  the  puddling  action  of  water,   (6)  the  pounding  of  hoofs 
and  wheels,  (c)  the  jarring  and  compressive  action  of  rolling 
artificially. 

4.  If  the  puddling  action  of  rains  is  the  only  factor,  a  loose 
mass  of  earth  will  shrink  slowly  back  to  its  original  volume, 
but  an  embankment  of  loose  earth  will  at  the  end  of  a  year  be 
still  about  j1^,  or  8  per  cent  greater  than  the  cut  it  came  from. 

5.  If  the  embankment  is  made  with  small  one-horse  carts, 
or  wheel  scrapers,  at  the  end  of  the  work  it  will  occupy  5  to 
10  per  cent  less  space  than  the  cut  from  which  the  earth  was 
taken,  and  in  subsequent  years  will  shrink  about  2  per  cent 
more,  often  less  than  2  per  cent. 

6.  If  the  embankment  is  made  with  wagons  or  dump  cars, 
and  made  rapidly  in  dry  weather  without  water,  it  will  shrink 
about  3  per  cent  to    10  per  cent   in   the   year   following  the 
completion  of  the  work,  and  very  little  in  subsequent  years. 

7.  The  height  of  the  embankment  appears  to  have  little 
effect  on  its  subsequent  shrinkage. 

8.  By  the  proper  mixing  of  clay  or  loam  and  gravel,  followed 
by  sprinkling  and  rolling  in  thin  layers,  a  bank  can  be  made 
weighing  1}  times  as  much  as  loose  earth,  or  133  pounds  per 
cubic  foot. 

9.  The  bottom  lands  of  certain  river  valleys  and  banks  of 

*  "  Earthwork  and  Its  Cost,"  by  H.  P.  Gillette,  page  17. 


58  THE  ART  OF  ROADMAKING 

cemented  gravel  or  hardpan  are  more  than  ordinarily  dense 
and  will  occupy  more  space  in  the  fill  than  in  the  cut  unless 
rolled. 

The  natural  shrinkage  of  the  ordinary  soils  is  in  the  following 
order,  beginning  with  the  least:    (1)  sand  and  sandy  gravel, 

(2)  clay  and  clayey  soils,  (3)  loams;    and  according  to  the 
method    of    handling:     (1)    dragscrapers,    (2)    wheelscrapers, 

(3)  wagons,  (4)  cars,  (5)  wheelbarrows. 


FIG.  18  shows  an  embankment  made  in  the  customary  manner  by  dump- 
ing material  mainly  in  the  center  of  the  roadway  and  sloping  it  to  the 
right  and  left  by  the  usual  means,  leaving  it  always  higher  in  the 
center  and  with  a  tendency  to  slide  off  at  both  sides. 

In  making  embankments,   materials  are  used  which  have 
the  greatest  frictional  stability,  such  as  rock,  shingle,  gravel 
and  clean  sand;    wet  clay  and  mud  are  entirely  unsuitable. 
The  cheapest  and  quickest  method  of  building  the  embank- 
ment is  by  making  it  of  a  single  layer,  but  in  certain 
bailments'  sPec^a^  cases>  sucn  as  filling  in  behind  a  retaining 
wall   and   bridge   abutments,   the   embankment   is 


FIG.  19  shows   the  method    in  which    the  material  has  been  deposited 
properly  and  the  surface  kept  hollowed  until  finished. 

made  in  thin  horizontal  layers,  9  to  18  inches  deep,  each 
rolled  and  rammed  down  so  as  to  make  it  co'mpact  and  firm 
before  laying  down  the  next  layer. 

Specifications  usually  require  that  "all  matter  of  vegetable 
nature  be  carefully  excluded  from  the  embankment,"  but 
this  is  sometimes  impracticable.  It  is  desirable  that  all 
stumps,  weeds,  brush,  etc.,  are  removed  from  the  space  to  be 


CONSTRUCTION  AND  PROTECTIVE  WORKS 


59 


occupied  by  the  embankment  as  well  as  all  deposits  of  soft 
compressible  matter,  in  order  to  give  it  a  firm  base  and  to 
permit  it  to  bond  with  the  earth  below.  To  overcome  the 
tendency  to  spread,  a  small  trench  is  sometimes  excavated 


FIG.  20. — Method  of  Construction  on  Slopes  by  Embankment. 

along  the  foot  of  the  embankment,  or  it  may  be  buttressed 
with  a  low  stone  wall. 

When  a  roadway  is  built  on  the  side  slope  of  a  hill,  partly 
by  excavating  and  partly  by  embanking,  the  most  common 
method  is  to  build  the  embankment  out  gradually  along  the 
whole  line  of  the  excavation.  This,  however,  is  insecure, 


FIG.  21. — Method  of  Construction  on  Slopes  by  Stepped  Embankment. 

as  the  excavated  material,  if  simply  deposited  on  the  natural 
slope,  is  liable  to  slip.  It  should  be  given  a  secure  hold, 
particularly  at  the  foot  of  the  slope,  by  cutting  the  natural 
surface  into  steps  perpendicular  to  the  axis  of  greatest  pressure. 


60 


THE  ART  OF  ROADMAKING 


But  on  side  hills  of  great  inclination,  retaining  walls  must  be 
substituted  for  the  side  slopes  of  both  the  excavations  and 
the  embankments  (see  page  88). 

On  rock  slopes  where  the  inclination  of  the  natural  surface 
is  not  greater  than  1:2  the  road  may  be  constructed  partly 
in  excavation  and  partly  in  embankment  in  the  usual  manner 


FIG.  22. — Method  of  Construction  on  Slopes,  using  Retaining  Walls. 

as  outlined,  but  when  the  rock  slope  has  a  greater  inclination 
than  1 : 2  the  whole  of  the  roadway  should  be  in  excavation  as 
shown  in  Fig.  24.  Roads  on  rock  slopes  may  also  be  built 
in  the  form  of  a  platform  on  timber  frameworks  supported  by 
beams  and  struts. 


FIG.  23.  FIG.  24. 

Method  of  Construction  on  Rock  Slopes. 

In  constructing  embankments  across  wet  and  unstable 
ground  it  is  frequently  necessary  to  form  an  artificial  founda- 
tion upon  which  to  place  the  earth  embankment.  This  may 
be  accomplished  in  some  cases  by  excavating  a  little  of  the 
soft  material  and  substituting  sand  or  gravel,  or  in  other 
cases  it  may  be  advisable  to  employ  layers  of  brushwood  or 


CONSTRUCTION  AND   PROTECTIVE  WORKS 


61 


fascines  as  a  support  for  the  embankment.  Sometimes  it 
may  be  possible  to  drain  the  soft  material  by  deep  ditches, 
so  as  to  render  it  capable  of  sustaining  the  road,  and  in  all 
cases  drainage  should  be  provided  in  so  far  as  possible  to  make 
the  embankment  more  secure. 


(From  Coane's  "Australasian  Roads  ") 

FIG.  25. — Road  entirely  in  Rock  Cut.     Hawk's  Crag,  Buller  Gorge, 
New  Zealand. 

Earthwork  is  paid  for  by  the  cubic  yard,  usually  measured 
"in  place/'  that  is,  in  the  natural  bank,   cut,   or 
pit,  before  loosening,  the  cost  being  based  on  the 
daily  wages   of   a  common  unskilled  laborer.     This 
cost  may  be  divided  into  three  parts: 


62  THE  ART  OF  ROADMAKING 

1.  Cost  of  loosening  the  earth,  depending  on  the  kind  of 

earth  to  be  handled. 

2.  Cost  of  transport,  depending  on  the  quantity  of  material 

to  be  moved,  the  distance  of  haulage  and  the  kinds  of 
roads  over  which  it  must  be  hauled. 

3.  Cost    of   transforming   the    transported    earth    into    the 

desired  shape. 

It  is  necessary,  therefore,  to  study  the  various  methods  of 
loosening  and  handling  the  various  kinds  of  materials  and 
their  costs,  and  the  relative  economy  of  moving  earth  with 
a  shovel,  or  transporting  it  by  wheelbarrow  or  horse  cart,  which 
involve  more  questions  than  could  be  taken  up  satisfactorily 
within  the  limits  of  a  few  pages. 

The  calculation  of  earthwork  forms  a  large  part  of  the 
necessary  labor  of  the  engineer,  and  to  relieve  him  of  the 
tediousness  of  this  work,  as  well  as  to  facilitate  its  operation, 
many  tables,  diagrams,  and  approximate  formula)  have 
been  devised,  no  one  of  which  has,  however,  met  with  general 
favor  by  engineers.  Several  publications  dealing  with  these 
methods  of  calculations  are  listed  in  the  bibliography  in 
Appendix  V. 

FOUNDATION  AND  DRAINAGE 

In  building  any  roadway,  whether  for  the  city  or  the  country, 
for  light  or  heavy  traffic,  two  of  the  most  important  points  to 
be  considered  are  drainage  and  foundation. 

Theoretically,  the  foundation  should  last  forever,  and  the 
sole  cost  of  maintenance  should  be  borne  by  the  wearing 
surface,  but  this,  for  economical  reasons,  is  difficult  of  realiza- 
tion. The  light  traffic  roadway  of  to-day,  requiring  for 
foundation  only  four  inches  of  broken  stone,  may  be  the  heavy 
traffic  street  of  to-morrow,  requiring  six  inches  of  Portland 
cement  concrete.  The  advent  of  the  pleasure  and  the  industrial 
automobile  is  bringing  upon  the  macadam  roads  of  the  country 
far  greater  weight  than  was  imagined  by  the  original  builders 
of  these  roads,  and  it  is  only  a  question  of  time  when  it  may 
be  necessary  to  reconstruct  many  of  these  roadways  from  the 
bottom  up  with  a  firm  concrete  foundation. 


CONSTRUCTION  AND  PROTECTIVE  WORKS 


63 


In  building  new  roads,  future  traffic  should  be  taken  into 
account,  and  a  foundation  sufficient  for  all  reasonable  develop- 
ment should  be  provided.  The  stability  of  the  road  surface 
depends  upon  the  foundation  and  this  in  turn  largely  depends 
upon  the  facilities  provided  for  drainage.  While  proper 


^y^w^^^^ww^ 

b.  Road  in  Embankment. 


I6'0" - 10'  0"- 


c.  Suburban  Street. 
FIG.  26.— Methods  of  Drainage. 

attention   may   be   given   to   surface   drainage   by   providing 
sufficient  crown  to  shed  the  water  and  ditches  to 
carry  it  away,  the  importance  of  subdrainage  is   The  imP°r- 
often  overlooked.     Its  necessity  must  be  realized,    Drainage, 
as  a  permanent  foundation  can  be  secured  only  by 
keeping   the  subsoil  dry;    unless  this  is    done,  and  water  is 
kept  out  of  the  foundation,  sooner  or  later  it  will  destroy  the 
superstructure.     Most  earths,  when  kept  dry,  form  a  strong 
foundation,  but  when  the  ground  is  naturally  wet  a  good  road 
cannot   be   constructed   without   proper   subdrainage,    as   the 
earth  loses  its  sustaining  power  and  the  formation  goes  to 
pieces.     Where  the  soil,  however,  is  sandy  or  calcareous,  or 


64 


THE  ART  OF  ROADMAKING 


FIG.  27.— Types  of  Drains. 

Pole  Drain  Blind  Drain  Stone  Drain 

Silt  Basin  Tile  Drain  Silt  Basin 

Outlet 


CONSTRUCTION  AND  PROTECTIVE  WORKS  65 

where  the  subsoil  consists  of  fairly  open  gravel,  underdrains 
are  seldom,  if  ever,  required. 

Drainage  is  especially  important  upon  earth  roads,  because 
the  material  of  the  road  surface  is  more  susceptible  to  the 
action  of  the  water,  and  more  easily  destroyed  by  it  than  are 
the  materials  used  in  the  construction  of  the  better  class  of 
roads.  When  water  is  allowed  to  stand  upon  the  road  in 
ruts  and  hollows,  the  earth  is  softened  and  readily  penetrated 
by  the  wheels,  which  continually  deepen  and  enlarge  the 
ruts  until  the  whole  crust  of  the  road  and  the  subsoil  beneath 
is  weakened.  The  action  of  frost  is  also  apt  to  be  more 
disastrous  upon  the  more  permeable  surface  of  the  earth  road, 
having  an  effect  to  swell  and  heave  the  roadway  and  throw  its 
surface  out  of  shape.  It  may,  in  fact,  be  said  that  the  whole 
problem  of  the  improvement  and  maintenance  of  ordinary 
country  roads  is  one  of  mere  drainage.  A  road  on  a  wet 
undrained  bottom  will  always  be  troublesome  and  expensive 
to  maintain,  and  it  will  be  economical  in  the  long  run  to  go  to 
considerable  expense  in  making  the  drainage  of  the  subsoil  as 
perfect  as  possible. 

There  are  three  systems  of  drainage:  underdrainage,  side 
ditches,  and  surface  drainage: 

The  objects  of  underdrainage  are: 

1.  To  lower  the  water  level  in  the  soil  and  get  it 

away  from  the  foundations.  The  action  of 
sun  and  wind  will  dry  the  surface  of  the  road,  but  if  the 
foundation  is  soft  and  spongy  the  road  will  soon  become 
a  mass  of  mud. 

2.  To  dry  the  ground  quickly  after  a  freeze.     When  the 

frost  comes  out  of  the  ground  in  the  spring,  it  thaws 
quite  as  much  from  the  bottom  as  from  the  top  and  with 
proper  underdrainage  the  water,  when  released  by 
thawing  from  below,  will  be  immediately  carried 
away. 

3.  To  remove  the  "underflow."     In  some  places  when  the 

ground  is  comparatively  dry  when  it  freezes  in  the  fall,  it 
will  be  very  wet  in  the  spring  when  the  frost  comes  out. 
The  reason  is  that  after  the  ground  freezes,  water  rises 


66  THE  ART  OF  ROADMAKING 

slowly  in  the  soil  by  hydrostatic  pressure  of  the  water 
in  higher  places;  and  if  it  is  not  drawn  off  by  under- 
drainage  it  saturates  the  subsoil  and  rises  as  the  frost 
goes  out.  The  underdrainage  not  only  removes  the 


FIG.  28. — Methods  of  Drainage  of  Surface  Water  from  Country  Roads. 

On  roads  where  there  are  no  sidewalks,  gutters  are  formed  between  the 
roadway  and  the  pathway,  and  the  water  is  conducted  from  these  gutters 
into  the  side  ditches  by  pipes  laid  under  the  walk  at  intervals. 

water,  but  prevents,  or  reduces,  the  destructive  effects 
of  frost. 

The  object  of  side  ditches  or  gutters  is  to  receive  the  water 
from  the  surface  of  the  traveled  roadway,  and  they  should 


CONSTRUCTION  AND  PROTECTIVE  WORKS  67 

carry  it  rapidly  and  entirely  away  from  the  roadside.  They 
also  intercept  and  carry  off  the  water  that  would 

otherwise  flow  from   the   side  hills  upon   the  road.  'vSjJ*0! 

side  ditches. 
The  side  ditch  need  not  be  deep,  and  should  have 

a  broad  flaring  side  toward  the  roadway,  while  the  outside 
bank  should  be  flat  enough  to  prevent  caving.  It  should 
have  a  good  fall  and  a  free  outlet  into  some  stream  so  as  to 
keep  the  water  moving  and  to  carry  it  entirely  away  from  the 
road. 

Surface  drainage  of  the  traveled  portion  of  the  road  affects 
mainly  the  maintenance  of  the  road  and  is  fully  as 
important  as  the  underdrainage.  It  is  provided  for 
by  crowning  the  surface.  The  slope  from  the  center 
to  the  side  should  be  enough  to  carry  the  water  freely  and 
quickly  to  the  side  ditch. 


FIG.  29.— Profile  of  Road  Section. 

There  has  been  much  discussion  as  to  the  exact  crown  and 
slope  to  be  given  to  the  surface  of  the  roadway.  Some  claim 
that  the  shape  should  be  the  arc  of  a  circle,  others 

that    it  should  be  a  parabolic   arch  started  at  the    Tra°sversc 

contour, 
curb  line  or  at   the   edge  of    the    gutter,  and  still 

others  that  it  should  consist  of  two  planes  meeting  at  the 
center  and  having  their  junction  rounded  off  with  a  short 
curve.  The  last  two  forms  are  probably  better  than  the  first, 
but  great  refinement  in  this  matter  is  neither  possible  nor 
important. 

The  proper  crown  varies  with  the  nature  of  the  roadway; 
when  a  good  surface  is  maintained  a  very  moderate  rise  is 
sufficient,  but  in  all  cases  this  rise  should  bear  a  certain  propor- 
tion to  the  width  of  the  roadway,  as  shown  approximately  in 
the  accompanying  table: 


THE  ART  OF  ROADMAKING 


TABLE  VI 

AMOUNT  OF  TRANSVERSE  RISE  REQUIRED  FOR  DIFFERENT 
PAVEMENTS. 


Surface. 

Earth 

Rise  at  center  

Proportion  of  the 
width  of  roadway. 

l/40 

Gravel, 
Broken  stone 

<  t 

1/60 

Stone  Block, 
Wood, 
Brick, 

i  i 
(  i 

Vso 
Vioo 

Vso 

Asphalt, 

1  1 

Vso 

Although   the    curved   profile   is   universally   used,    no   set 
practice  in  respect  to  the  crown  exists.     In  some  places  asphalt 


FIG.  30.— Arrangements  of  Transverse  Grade  in  Cases  of  Streets  in  which 
the  Opposite  Sides  are  at  Different  Levels. 

is  given  the  smallest  crown  of  any  pavement,  while  in  others, 
notably  in  Omaha,  it  has  the  largest,  both  methods  seeming 
to  be  based  on  good  judgment,  the  former  on  the  smoothness 
of  the  surface  and  the  latter  on  the  fact  that  asphalt  rots  when 
continuously  wet. 


CONSTRUCTION  AND  PROTECTIVE  WORKS 


HIGHWAY  BRIDGES 

Of  the  money  spent  in  many  parts  of  the  country  on  the 
maintenance  of  a  highway  system,  nearly  one-half  is  expended 
in  the  construction  and  repair  of  culverts  and  bridges.  Espe- 
cially in  well-watered  areas  the  problem  of  keeping  these 
works  in  good  repair  is  one  of  considerable  difficulty.  In 
fact,  it  is  sometimes  more  necessary  to  spend  money  for  good 
bridges  than  for  good  roads.  Rarely  is  the  condition  of  a 
road  so  bad  that  it  stops  travel  entirely  or  becomes  actually 
dangerous  to  life  or  property,  as  happens  in  case  of  the  destruc- 
tion of  an  important  bridge. 

To  secure  the  safety  of  a  bridge  a  good  foundation  for  the 
substructure  is  of  the  highest  importance;  a  bridge  on  a  poor 
foundation  cannot  be  maintained.  If  the  stream  bed  be 
too  soft  to  support  the  substructure,  piles  should  be  driven; 
if  it  is  subject  to  wash  such  as  to  endanger  the  foundations, 
special  pains  should  be  taken  to  protect  the  foundations. 

In  building  a  permanent  structure  the  first  thing  to  be  con- 
sidered is  the  site  upon  which  it  is  to  be  erected,  which  should, 

if  possible,  be  in  a  location  where  the  bridge  will 

i          TXXI  -ui  •          •  Location, 

be  exposed  as  little  as  possible  to  the  various  in- 
fluences tending  to  cause  its  destruction.  It  should  be  so 
located  that  the  cost  of  construction  will  be  as  low  as  is  con- 
sistent with  good  service  to  the  public,  and  care  should  be 
observed  to  avoid  placing  the  bridge  at  a  point  where  a  stream 
is  apt  to  change  its  bed.  For  the  safety  of  the  public  the 
approaches  should  be  in  line  with  the  bridge  for  as  great  a  dis- 
tance as  possible  at  each  end,  especially  if  the  road  is  on  a 
grade. 

By  a  judicious  change  in  the  location  of  a  road,  bridges  can 
sometimes  be  avoided  without  inconvenience  to  the  public. 
Fig.  13  (page  50)  shows  a  case  in  which  there  are  three 
bridges  of  60-feet  span  over  a  stream  where  one  would  be 
sufficient  for  the  public  convenience. 

Highway  bridges  may  be  classed  according  to  the  materials 
of  which  the  superstructures  are  built,  as  follows: 


70 


THE  ART  OF  ROADMAKING 


FIG.  31. — Clariton-Clifton  Two-hinged  Arch  Highway  Bridge  Over 
Niagara  River. 


FIG.  32. — Suspension  Highway  Bridge  Over  Niagara  River. 
(From  "Design  of  Highway  Bridges,"  by  M.  S.  Ketchum) 


CONSTRUCTION  AND   PROTECTIVE  WORKS  71 

1.  Steel  or  iron. 

a.  Short  span;  6.  High  truss;  c.  Plate  girder. 

2.  Steel  or  iron  in  combination  with  timber. 

0     r~.     ,  Classmca- 

3.  Timber.  tion  of 

4.  Masonry  or  concrete.  highway 

a.  Arches;    6.  Beam;    c.  Culverts.  bridges. 

5.  Reinforced  concrete. 

There  are  locations  for  which  each  type  is  adapted.     In  the 
past,  the  cheapness  of  good  lumber,  the  ease  with  which  tim- 


(From  Wis.  Geological  Survey  Bulletin) 
FIG.  33. — The  Old  Style  Highway  Bridge. 

ber  bridges  could  be  built  and  repaired,  and  the  high  price 
of  other  materials  were  the  causes  for  the  wide  use  of  such  a 
perishable  material  as  timber,  but  in  recent  years  conditions 
have  changed;  lumber  has  increased  in  price  while  the  prices 
of  steel  and  Portland  cement  have  decreased.  Steel  is  the 
material  most  widely  used  and  is  used  for  bridges  of  all 
spans. 

A  bridge  truss  is  a  framework  composed  of  individual  mem- 
bers so  fastened  together  that  loads  applied  at  the 
joints  produce  only  direct  tension  or  compression. 
In  its  simplest  form  every  truss  is  a  triangle  or  a 
combination  of  triangles,  this  being  the  only  geometrical  figure 


72 


THE  ART  OF  ROADMAKING 


in  which  the  form  is  changed  only  by  changing  the  length  of  the 
sides.  The  members  of  the  truss  are  either  fastened  together 
with  pins,  termed  "pin-connected,"  or  with  plates  and  rivets, 
termed  "riveted." 

Fig.    34    represents    a    bridge    consisting    of     two    vertical 
trusses  which  carry  the  floor  and  the  load;    two  horizontal 


Portal  — 


/-       /        i<J>v    XV°5 
c-/- — ±-  -1^'  ic<,X 


JO* 

\rt 


™&  u^ 
V>^ 


(From  "Design  of  Highway  Bridges,"  by  M.  S. 
-*^     \j|(/"  '  Ketchum) 

FIG.  34. — Diagrammatic  Sketch  of  a  Through  Pratt  Truss  Highway 

Bridge. 


trusses  in  the  planes  of  the  top  and  bottom  chords,  respectively,, 
which  carry  the  horizontal  wind  load  along  the  bridge;  and 
cross-bracing  in  the  plane  of  the  end-posts,  called  "portals," 
and  in  the  plane  of  the  intermediate  posts,  called  "  sway 
bracing."  The  floor  is  carried  on  joists  placed  parallel  to  the 
length  of  the  bridge,  and  which  are  supported  in  turn  by  the 
floorbeams.  The  main  ties,  hip  verticals,  counters  and  inter- 
mediate posts  are  together  called  "webs."  The  bridge  shown 


CONSTRUCTION  AND   PROTECTIVE  WORKS 


73 


in  Fig.  34  is  a  "through  pin-connected"  bridge  of  the  "Pratt" 
type,  the  traffic  passing  through  the  bridge.  Short-span 
highway  bridges  have  low  trusses  and  no  top  lateral  system 
or  portals. 

The  simplest  type  of  bridge  is  the  "  beam "  bridge  (a)  Fig. 


(a)  Beam  Bridge 


(d)Lowk/arren  Truss. 


(b)  Beam  L  egdncfge.       (e)  Low  Pratt  Truss.  Half  Hip. 


ESI 


(c)  Truss  Leg  bridge. 


(f)  L  ow  Pratt  Truss.  Full  5 I  ope. 


(From  "  Design  of  Highway  Bridges,"  by  M.  S.  Ketchum) 
FIG.  35. — Types  of  Short  Span  Highway  Bridges. 


span 


the 


TyPes  of 
™       *' 


35.     This    commonly   consists   of    I-beams   which 

opening,   and  are  placed  near  enough  together  to 

carry  the  floor  of  the  bridge.     Where  foundations 

are  relatively  expensive  the  beams  may  be  carried 

on  posts  as  in  (6).     A  "Truss  Leg"  bridge  is  shown 

in    (c).     A    "Warren"    truss    is    a    combination    of    isosceles 

triangles  as  shown  in  (d).     The  "Pratt"  truss  has  its  vertical 

web  members  in  compression  while  its  diagonal  web  members 


74 


THE  ART  OF  ROADMAKING 


are  in  tension,  as  shown  in  (e)  and  (/).  The  "Warren"  truss 
is  commonly  built  with  riveted  joints  while  the  " Pratt"  truss 
is  usually  built  with  pin-connected  joints.  The  "Warren" 


FIG.  36.— Through  Howe  Truss. 

low  truss  with   riveted   joints   as   shown  in    (d)    is   generally 
preferable  to  the  low  "Pratt"  truss  in  either  (e)  or  (/). 
The  "  Howe  "  truss  has  its  vertical  web  members  in  tension, 


FIG.  37.— Baltimore  Truss. 

and  its  inclined  web  members  in  compression,  as  in  Fig.  36. 
The  upper  and  lower  chords  and  the  inclined  members  of  a 
"Howe"  truss  are  commonly  made  of  timber,  while  the 
vertical  tension  members  are  iron  or  steel  rods. 


FIG.  38.— Petit  Truss. 

The  "  Whipple  "  truss  is  a  double  intersection  "  Pratt "  truss. 
This  was  designed  to  give  short  panels  in  long  spans  which 
have  a  considerable  depth. 


CONSTRUCTION  AND   PROTECTIVE  WORKS 


75 


The  " Baltimore"  truss  is  a  "Pratt"  truss  with  parallel 
chords  in  which  the  main  panels  have  been  subdivided  by  an 
auxiliary  framework  as  in  Fig.  37.  The  "Baltimore"  truss 
with  inclined  upper  chords,  is  called  a  "Petit"  truss. 


FIG.  39.— Typical  Leg  Bridge. 

Short    span  highway  bridges    include   beam,  leg   and  low- 
truss  bridges. 

Beam  bridges  are  made  by  placing  steel  beams  side  by  side 


FIG.  40.  (a)  and  (6). — Illustrating  Deflection  of  Supports  of  Leg  Bridge. 

Fig.  40  (a),  a  shows  the  position  of  the  top  of  the  upright  leg  at  time  of  erection, 
with  fall  of  temperature,  the  floor  joists  shorten  ami  the  legs  assume  the  new  position  b; 
With  increase  in  temperature  the  tops  of  the  legs  are  forced  back  towards  their  original 
positions,  and  the  bank  is  compelled  to  yield  to  their  pressure,  but  mainly  at  the  top. 
The  legs  will  then  assume  the  curved  position  c  in  Fig.  40  (6).  The  tendency  of  the 
curved  beam  to  straighten  throws  the  foot  out  and  the  leg  takes  a  step  into  the  stream 
the  final  position  being  shown  at  d.  This  process  is  repeated  with  every  recurring  change 
of  temperature. 

with  the  ends  resting  in  the  abutments.     The  roadway  floor 

is  usually  made  of  planks  laid  transversely  on  top 

of  the  beams.     The  spacing  of  the  beams  depends 

on  the  load  to  be  carried  and  upon  the  thickness 

of  the  floor  planks,  for  which  a  common  rule  is  that  the  plank 


76 


THE   ART   OF  ROADMAKING 


FIG.  41. — A  Warren  Low  Truss  Highway  Bridge. 


FIG.  42.— A  Pratt  Low  Truss  Highway  Bridge;  Seven  100-it.  Spans. 


CONSTRUCTION  AND   PROTECTIVE  WORKS 


77 


shall  have  at  least  one  inch  in  thickness  for  each  foot  of  spacing 
of  the  joists  or  stringers.  The  outside  beams  carry  a  smaller 
load  than  the  intermediate  beams  and  are  usually  steel  channels, 
while  the  intermediate  beams  are  steel  I-beams  having  a  depth 
of  about  ^Q  of  the  span. 

Beam  and  truss  bridges  are  sometimes  supported  on  steel 
legs  in  the  place  of  abutments,  and  should  be  designed  to 
carry  the  thrust  of  the  filling  in  addition  to  the  live  and  dead 
load  on  one-half  of  the  span.  Unless  very  carefully  designed 
and  constructed,  leg  bridges  are  inferior  structures  and  are  not 
to  be  recommended. 


FIG.  43.— A  Pratt  Low  Truss  Bridge  40-ft.  Span  with  Concrete  Floor. 

Low-truss  bridges  are  used  for  spans  of  from  30  to  80  feet, 
and    special   designs    to    about    100   feet.     The    trusses    may 
have  either  pin-connected  or  riveted  joints;  they 
may  have  either  half-hips,  or  full  slopes,  and  may     J^'^j1 
be  either  of  the  "Warren"  or  the  " Pratt"  type. 

High-truss  bridges  with  spans  of  from  80  to  170  feet  are 
built  with  parallel  chords  and  with  either  pin-connected  or 
riveted  joints;  with  spans  of  from  160  to  220  feet, 
they  are  usually  built  of  the  "Pratt"  type  with 
inclined  upper  chords  trusses;  with  spans  above 
220  feet,  bridges  are  usually  built  with  the  "Petit"  type  of 


78 


THE  ART  OF   ROADMAKING 


FIG.  44. — Cantilever  Highway  Bridge. 


FIG.  45. — Plate  Girder  Highway  Bridge. 

(From  "  Design  of  Highway  Bridges,"  by  M.  S.  Ketchum.) 


CONSTRUCTION  AND  PROTECTIVE  WORKS  79 

truss.      High-truss    pin-connected    bridges    should    never    be 
built  with  less  than  five  panels. 

A  "plate  girder"  consists  of  a  vertical  steel  or  iron  web 
plate  to  whose  top  and  bottom  edges  are  riveted  horizontal 
pairs  of  angles  to  form  flanges,  and  to  whose  ends 

are   attached   vertical   angles   which   transmit   the  ^>1f]te~girder 

bridges. 
load  to  the  supports. 

A  plate-girder  highway  bridge  consists  of  two  or  more, 
usually  two,  plate  girders  fastened  together  by  lateral  bracing. 
The  roadway  is  carried  on  a  floor  system  supported  near  the 
bottoms  of  the  plate  girders.  Short  spans  up  to  70  or  80 
feet  have  one  end  fixed  while  the  other  end  is  allowed  to  move 
on  a  sliding  plate.  For  greater  lengths  of  span  the  expansion 
end  is  supported  on  nests  of  rollers.  The  ordinary  limit  of 
plate-girder  spans  is  about  100  feet. 

Timber  was  formerly  quite  generally  used  in  the  construction 
of  highway  bridges,  and  is  still  used  for  temporary  structures 
in  locations  where  timber  is  cheap  and  iron  and 
steel  are  relatively  expensive.  It  is  used  in  (1)  Useoftim- 
timber  trestles,  (2)  timber  bridges  and  (3) 
combination  bridges,  in  which  the  top  chords 
and  intermediate  parts  are  made  of  timber  while  the  tension 
members  are  made  or  iron  or  steel. 

Wooden  bridges  are  expensive  to  maintain,  and,  where 
built  strong  enough  to  carry  heavy  loads  their  first  cost  is 
high.  They  are  dangerous,  since  they  will  often  give  way 
without  showing  any  signs  of  weakness. 

When  properly  constructed,  masonry  and  concrete  bridges 
are  permanent,  and  this  type  of  structure  should  be  given 
the  preference  when  conditions  are  favorable  for 
its   construction.  Masonry  and 

Stone  arches    have    been    built    from    time  im-          s 


memorial,  and  while  many  existing  arches  are 
standing  after  hundreds  of  years  it  is  equally  certain  that  many 
have  fallen  down.  Rightly  built  they  are  permanent,  since 
there  is  nothing  to  decay,  and  to  break  them  down  it  is  neces- 
sary to  crush  the  rock  of  which  they  are  built. 

Reinforced  concrete  beam  bridges  for  short  spans  up  to  15 


80 


THE    ART    OF    ROADMAKING 


FIG,  46.— Reinforced  Concrete  Bridge,  20-ft.  Span. 


FIG.  47.— Timber  Box  Culvert. 


FIG.  48.-  -Timber  Culvert. 


-    -  60 


FIG.  49.— Endwalls  for  Pipe  Culverts. 


CONSTRUCTION  AND  PROTECTIVE  WORKS 


81 


to  20  feet  are  commonly  made  of  a  single  slab  of  uniform 
thickness  spanning  the  opening.  For  longer  spans  the  floor 
system  is  made  of  deeper  horizontal  girders  supporting  a 
relatively  thin  floor  slab. 


FIG.  50.— A  Well  Built  Concrete  Culvert. 


FIG.  51. — A  concrete  culvert  cracked  a  few  days  after  being  built,  due  to 
the  concrete  not  being  thoroughly  mixed  and  tamped. 

Culverts  are  made  of  timber,  vitrified  clay  brick,  cast  iron 
pipe,    brick,    stone,    concrete,    and   reinforced    concrete.     For 
temporary  culverts  the  timber  box  may  be  used, 
the  bottom  being  paved  to  prevent  scour.     Care 
should  be  used  to  tamp  the  filling  to  prevent  water  flowing 


82  THE  ART  OF  ROADMAKING 

along  the  sides.  Timber  culverts  are  very  unsatisfactory  and 
in  the  long  run  are  very  expensive.  Pipe  culverts  should  be 
laid  on  a  firm  foundation  and  to  a  careful  grade.  The  center 
should  be  raised  so  that  there  will  be  no  hollows  in  the  pipe. 
Head  walls,  preferably  of  masonry  or  concrete,  should  ex- 
tend high  enough  to  carry  the  fill,  and  should  be  carried 
down  far  enough  to  prevent  the  water  from  following  along 
the  outside  of  the  pipe,  which  should  preferably  be  laid  in 
concrete. 

The  location  of  culverts  should  also  have  careful  considera- 
tion; often  they  are  built  and  maintained  where  they  are 
unnecessary.  It  is  of -no  benefit  to  carry  water  across  a  road 
in  a  culvert  unless  it  can  be  carried  away  from  the  road  at  that 
point;  it  should  be  carried  along  a  road  as  long  as  its  volume 
does  not  become  so  great  as  to  cause  serious  washing.  Culverts 
should,  of  course,  be  built  with  a  view  to  permanency,  and 
they  should  be  protected. 

An  important  feature  in  the  planning  of  a  bridge  or  culvert 

is  the  making  of  a  careful  estimate  of  the  amount  of  water 

for  the  passage  of  which  it  is  necessary  to  provide. 

openin          ^n*s  *s  alwavs  done  by  railroad  companies  in  planning 

their    structures   and    should   be   done   for    every 

highway  structure  as  well. 

The  amount  of  water  that  will  come  from  a  certain  drainage 
area  and  flow  through  any  culvert  or  under  any  bridge  in  a 
given  amount  of  time  can  be  determined  only  in  a  general  way 
and  rarely  with  any  high  degree  of  accuracy,  as  it  depends 
upon  too  many  factors.  These  are: 

1.  Area  of  drainage  basin. 

2.  Maximum  rainfall  per  hour. 

3.  Slope  of  the  surface. 

4.  Character  of  the  soil — porous  or  compact. 

Some  of  the  more  important  of  these  factors  are  practically 
unknown,  as  even  the  most  carefully  kept  weather  records 
seldom  give  the  rainfall  for  each  shower,  which  is  the  point  of 
importance  in  determining  the  amount  of  water  to  be  provided 
for.  The  amount  of  water  which  the  soil  will  absorb  may 
vary  from  a  small  percentage  to  almost  the  whole  amount  of  the 


CONSTRUCTION  AND  PROTECTIVE  WORKS  83 

rainfall,  depending  on  its  conditions  at  the  time  of  the  shower. 
Floorbeams  for  highway  bridges  are  made  of  rolled  I-beams 
or  riveted  plate  girders,  and  may  be  riveted  to  the  posts  or 
hung  from  the  lower  chord  pins.     Joists  or  stringers 

are  made  either  of  rolled   I-beams   or  of  timber.      °°™eams 

and  floors. 
The  floors  are  made  of  timber,  reinforced  concrete, 

bent  steel  or  iron  plates  or  bars,  or  angles  and  plates  rilled 
with  concrete. 

In  the  past  steel  bridges  have  generally  been  built  with 
plank  floors,  but  the  increase  in  the  price  of  lumber  has  re- 
sulted in  the  use  of  the  more  substantial  materials  which  will 
endure  as  long  as  the  bridge. 

In  any  type  of  bridge  it  is  of  the  utmost  importance  that 
the  superstructure  be  well  supported.  If  this  is  not  done  the 
best  bridge  that  can  be  constructed  will  fail.  When 
an  arch  fails  it  is  generally  because  the  foundation  st"u~  tures 
has  settled.  In  the  case  of  steel  structures,  failures 
are  often  the  result  of  failures  in  the  substructure.  These 
bridges  are  designed  to  withstand  certain  forces  applied  in 
certain  ways.  So  long  as  the  bridge  rests  securely  upon  the 
substructure,  the  conditions  expected  in  the  design  are  ful- 
filled, but  if  the  structure  settles  to  any  great  extent,  strains 
which  are  entirely  unexpected  and  consequently  not  provided 
for  in  the  design  are  introduced,  and  though  the  bridge  may 
not  fail  all  at  once  its  joints  become  loose,  the  trusses  get  out 
of  line,  the  bars  begin  to  rattle  badly  when  any  considerable 
load  crosses,  and  the  structure  weakens  much  more  rapidly 
than  under  ordinary  conditions.  The  forms  of  substructures 
ordinarily  employed  are  abutments  and  piers  of  stone  or 
concrete,  and  steel  piling. 

An  abutment  is  a  structure,  commonly  made  of  masonry, 
that  supports  the  ends  of  the  bridge  and  acts  as  a  retaining 
wall   to   hold   back   the   earth   fill.      A   pier   is   a 
structure  that  supports  the  ends  of  the  bridge  where 
there  is   no  filling  to  support.     Abutments  and  piers  are  gen-- 
erally  at  right  angles  with  the  center  line  of  the  bridge.     A 
bridge  in  which  the  abutments  are  not  at  right  angles  to  the 
center  line  is  called  a  "  skew "  bridge. 


84 


THE  ART    OF  ROADMAKING 


Transverse  Section. 

FIG.  52, — Beam  Bridge  with  Solid  Floor. 


jEMb.NCWS. 


j< -  2'6  "-  f  •//>•—      ' TlO"- 

FIG.  53. — Details  of  Concrete  Floor. 


CONSTRUCTION  'AND  PROTECTIVE  WORKS 


85 


FIG.  54. — A  Substructure  of  Five  Light  I-beams  with  a  Backing  or 
"Abutment"  of  Planks  which  will  have  to  be  Renewed  Every  Few 
Years. 


(From  "  Design  of  Highway  Bridges,"  by  M.  S.  Ketchum) 

FIG.  55. — Concrete  Abutments  for  111'  6"  Span  Steel  Riveted  Highway 
Bridge  Across  Illinois  and  Mississippi  Canal. 


86  THE  ART   OF  ROADMAKING 

Abutments  are  made  with 

1.  A  straight  main  section  without  wings. 

2.  Wings  making  an  angle  of  from  30  to  45°  with  the  axis 

of  the  stream. 

3.  A  T-section;  the  stem  of  the  T  running  back  into  the  fill. 

4.  A  U-section  where  the  wings  make  an  angle  of  90°  with 

the  axis  of  the  stream. 

Highway  bridge  abutments  /are  usually  made  with  wing- 
walls,  the  wings  making  an  angle  of  30  to  45°  with  the  face  of 
the  abutment.  The  abutment  with  wing  walls  holds  the  filling 
and  gives  a  freer  channel  than  any  of  the  other  types. 


(From  Wis.  Geological  Survey  Bulletin) 

FIG.  56.— The  Result  of  Flimsy  Construction. 

While  abutments  of  stone  or  concrete  are  practically  unaf- 
fected by  decay  they  may  be  destroyed  by  undermining.  The 
foundation  should  always  be  at  such  a  depth  that  there  will 
be  no  danger  of  wash,  and  if  in  soft  ground ,  piles  should  be 
driven.  One  great  advantage  of  stone  or  concrete  abutments 
over  all  other  structures  is  that  they  serve  as  retaining  walls 
and  permit  embankments  to  be  made  right  up  to  the  end  of 
the  bridge.  When  built  with  suitable  wing  walls  the  embank- 
ments are  well  protected  against  washing. 


CONSTRUCTION  AND  PROTECTIVE  WORKS  87 

The  most  economic  bridge  is  the  one  which  in  the  long  run 
will  give  the  best  service  and  cost  the  least  money,  taking  as 
a  measure  of  the  cost  the  amount  of  money  which 
it   will   be   necessary   to    capitalize   in   order   that      Most 
the  interest  may  pay  for  (1)  the  maintenance  and 
repairs,  (2)  the  interest  on  the  first  cost,  and  (3)  a 
sinking  fund  for  depreciation  so  that  the  bridge  may  be  re- 
placed when  it  is  no  longer  fit  for  the  service  demanded. 

The  possible  life  of  any  particular  bridge  is  difficult  to 
estimate.  Steel  bridges,  if  properly  constructed,  should  last 
from  25  to  40  years;  combination  bridges,  from  10  to  15  years, 
while  masonry  and  reinforced  concrete  bridges  are  ordinarily 
considered  as  permanent  structures.  Timber  floors  must  be 
replaced  in  3  to  5  years,  and  steel  bridges  should  be  painted 
every  3  to  4  years.  Hence  the  first  cost  of  a  bridge  is  not  a 
safe  criterion  upon  which  to  base  economy.  Much  money  is 
wasted  in  putting  in  cheap,  flimsy,  bridges  which  are  short- 
lived, unsatisfactory  and  are  continually  in  need  of  repairs. 

RETAINING  WALLS 

A  retaining  wall  is  a  structure  that  retains  the  lateral 
pressure  of  the  earth  on  hillsides.  The  pressure  of  the  material 
supported  varies  considerably,  depending  upon  the  material,  the 
manner  of  depositing  it  in  place,  and  upon  the  amount  of 
moisture.  If  dry  clay  is  loosely  deposited  behind  the  wall 
it  will  exert  the  full  pressure  due  to  this  condition.  In  time 
the  earth  becomes  consolidated  and  cohesion  and  moisture 
make  a  solid  clay,  which  often  causes  the  bank  to  shrink 
away  from  the  wall,  and  there  will  be  no  pressure  exerted. 
On  the  oth?r  hand,  if  a  considerable  amount  of  water  is  added, 
the  normal  pressure  rapidly  increases  and  approaches  that 
due  to  a  liquid  having  the  same  specific  gravity. 

Retaining  walls  should  be  built  on  steep  hillsides  and  moun- 
tain roads — 

1 .  At  all  re-entering  curves.  Where  re- 

2.  At  all  culverts  and  bridges.  areTbuilk* 

3.  On  the  edge  of  all  precipitous  places. 

4.  When  the  bank  slope  and  the  ground  slope  are  nearly  or 

quite  parallel  to  each  other. 


88  THE  ART    OF  ROADMAKING 

5.  Where  a  bank  would  be  of  excessive  length  owing  to 

the  angle  of  the  natural  ground  slope. 

6.  Where  a  wall  would  be  cheaper  than  a  bank. 

On  the  edges  of  dangerous  precipices,  when  there  is  a  heavy 


FIG.  57. — Road  Construction  on  Hillside,  with  Retaining  Walls. 


FIG.  58.— Surcharged  Wall. 

A  wall  is  said  to  be  "  surcharged  "  when  the  bank  it  retains  slopes  back- 
wards to  a  higher  level  than  top  of  the  wall. 

load  to  support,  the  walls  should  be  built  of  masonry,  but 
where  the  pressure  is  not  too  great  they  may  be  built  of  large 
stones  laid  dry.  They  should  be  carried  up  as  high  as  the 
natural  surface  of  the  ground  or  to  the  surface  of  the  roadway 


CONSTRUCTION  AND  PROTECTIVE  WORKS 


89 


and  a  parapet  wall  or  fence  raised  upon  it,  to  protect  pedes- 
trians against  accident. 

Dry  stone  retaining  walls  are  best  suited  for  roads  on  account 
of  their  self-draining  properties  and  their  cheapness. 

The  filling  back  of  the  wall  should  be  entirely  of  stone  if 
it  is  available.     Where  earth  is  used  it  should  be  deposited 
and  tamped  in  approximately  horizontal  layers  or 
in  layers  sloping  back  from  the  wall,  and  a  layer 
of  sand,  gravel,  or  other  porous  material  should  be  deposited 
between  the  fill  and  the  wall  to  drain  the  fill  downwards.     In 
case  of  masonry  retaining  walls,   to  insure  drainage  of  the 
filling,   drains   should  be  provided  back  of  the  footing  and 
"weep-holes"   should  be  provided  in  the  body  of  the  wall 


a.  Stepped  Profile. 


b.  Ogee  Profile. 
FIG.  59.— Sea  Walls. 


c.  Vertical  Profile. 


.at  frequent  intervals  to  allow  the  water  to  pass  through. 
The  filling  in  front  of  the  wall  should  also  be  carefully 
drained. 

Roads  along  the  seashore  are  protected  by  sea  walls,  which 
resist  the  wave  action  and  support  the  embanked  roadways. 
The  principal  weakness  of  most  sea  structures, 
especially  those  directly  opposed  to  the  action 
of  the  waves,  lies  in  the  liability  of  the  foundation 
to  wash  out.  To  provide  against  this  the  footings  should  be 
carried  well  down,  and  the  profile  of  the  wall  should  be  such 
as  to  break  up  the  waves  with  the  minimum  effect  on  the  foun- 
dations. 

The  stepped  profile  is  believed  to  accomplish  this  object 
better  than  any  other  form,  as  the  steps  break  up  the  waves, 


90  THE  ART  OF  ROADMAKING 

and  reduce  the  volume  of  water  likely  to  be  thrown  on  to  the 
roadway.  The  ogee  profile  looks  well  but  is  less  effective 
in  breaking  up  the  waves,  is  more  troublesome  to  construct, 
and  is  not  as  strong  as  the  other  forms.  The  vertical,  or 
nearly  vertical,  profile  is  used  in  locations  open  to  really  heavy 
seas. 


CHAPTER   VI 
MATERIALS   USED   IN  ROAD   CONSTRUCTION 

A  GREAT  variety  of  material  enters  into  the  construction  of 
present-day  roads  on  account  of  the  widely  varying  climatic, 
geologic  and  topographic  conditions  which  exist  in  this  country 
as  a  whole  and  almost  equally  so  of  any  particular  state  or 
locality.  Materials  which  might  be  used  with  economy  in 
one  locality  may  be  entirely  unserviceable  elsewhere  because 
of  excessive  cost  of  haulage.  This  forms  so  large  a  part  of 
the  cost  that  an  inferior  material  may  often  be  useful  econom- 
ically on  account  of  the  expense  of  securing  a  superior  material. 
In  general  it  may  be  stated  that  for  country  roads,  materials 
from  local  sources  must  be  employed. 

The  best  material  available  should  be  chosen,  and  if  not 
very  strong,  it  will  suffice  where  the  traffic  is  moderate,  a 
greater  quantity  making  up  for  want  of  durability, 
but  more  labor  will  be  required  to  keep  the  surface  ^°st  sult" 
of  the  road  in  proper  order  than  with  a  better  material. 
material.  With  heavier  traffic  the  use  of  a  better 
material,  even  at  a  higher  price,  becomes  more  advantageous, 
and  in  or  near  large  towns  the  best  material  at  almost  any 
price  is  generally  the  most  economical  in  the  end.  This  is 
especially  the  case  when  the  dirt  arising  from  wear  must  not 
only  be  scraped  off  constantly,  but  be  removed  altogether  from 
the  road.  Sometimes  a  stronger  and  more  costly  material 
may  be  used  for  the  surface  only,  the  body  of  the  road  being 
made  of  inferior  local  stone.  For  repairs,  the  better  material 
may  be  laid  only  on  the  middle  of  the  road,  where  the  wear 
is  the  greatest. 

In  the  making  of  new  roads,  and  to  a  greater  extent  in  the 
selection  of  the  most  suitable  spots  for  opening  the  necessary 
quarries  for  supplying  road-making  materials,  geology,  chem- 

91 


92  THE  ART  OF  ROADMAKING 

istry,  and  petrology  all  contribute  to  the  knowledge  necessary 
for  the  proper  scientific  study  of  the  materials.  While  observa- 
tion of  the  behavior  of  the  stones  in  a  road  may  be  more  con- 
vincing than  theoretical  knowledge,  time  is  necessary  for  such 
a  trial,  and  the  material  may,  after  all,  turn  out  to  be  defi- 
cient in  durability.  Experience  has  shown  that  even  in  the 
same  quarry,  remarkable  differences  exist  in  the  quality  of 
the  rock  which,  to  all  appearance,  is  of  a  similar  nature,  and 
it  is  only  by  a  microscopical  examination  of  the  rock  that 
these  peculiarities  and  the  diverse  wearing  properties  of 
different  rock-types  can  be  detected.  To  the  science  of 
petrology,  therefore,  must  the  road  engineer  look  for  that 
assurance,  which,  combined  with  a  study  of  the  physical  tests 
and  his  own  knowledge  of  the  actual  use  of  some  reliable  types 
of  road-stone,  will  insure  the  most  suitable  and  durable  ma- 
terial being  selected  for  any  particular  road. 

The   materials  most    commonly  used  for   roads  and   pave- 
ments are: 

1.  Stone,  in  the  form  of  blocks  and  broken  fragments. 

2.  Wood,  in  the  form  of  blocks  and  planks. 

3.  Asphalt  in  two  forms i  sheet  and  block. 

4.  Concrete. 

5.  Sand. 

6.  Clay. 

7.  Gravel. 

8.  Bituminous  materials  (other  than  sheet  and  block  asphalt). 

In  order  to  determine  the  fitness  of  the  different 
material1  °    materials  under  any  given  conditions  of  service,  it 
is  necessary  to  know: 

1.  The  agencies  causing  their  destruction. 

2.  The  extent  and  character  of  the  traffic. 

3.  The   topographic   and   climatic   conditions   under   which 
they  are  to  be  used. 

4.  The  properties  which  the  materials  must  possess  in  order 
to  resist  the  destroying  agencies. 

5.  The  most  reliable  method  of  ascertaining  experimentally 
the  extent  to  which  the  materials  possess  the  required  properties. 

Other   things   being   equal,    the   endurance   of    a   roadbed 


MATERIALS  USED  IN  ROAD  CONSTRUCTION  93 

depends  upon  the  qualities  of  the  materials  used,  assuming 
the  road  to  be  properly  constructed  and  adequately  A      des 
drained.     A  road  is  subject  to  attack  and  conse-  causing  de- 
quent  loss  of  material  in  part  by  reason  of   the  struction  of 
composition   of   that    material.     The    other   forces  roads' 
operating  upon  the  surface  to  destroy  the  road  or  pavement 
are:    (1)  physical,  (2)  mechanical  or  dynamical,  (3)  chemical, 
(4)    organic.     It   is   estimated   that   the   mechanical   agencies 
cause  80  per  cent  of  the  destruction  arid  the  others  20  per 
cent. 

The  physical  agencies  are: 

1.  The  disrupting   effects  of   frost  and  ice,  both 

on  the   integrity  of  the  road  bed  as  a  whole  and      a  ^nctes 
on  the  individual  rock  fragments  and  minerals. 

2.  The  transporting  power  of  water. 

3.  The  transporting  power  of  the  winds. 

4.  Heat  due  to  changes  of  temperature. 

5.  The  attrition  and  effect  of  falling  rain. 

6.  Gravity. 

It  has  been  the  object  of  the  highway  engineer  ever  since 
the  days  of  Macadam  to  construct  a  road  in  such  a  manner  that 
frost  action  above  subgrade  may  be  reduced  to  a  minimum. 
Macadam  contended  strenuously  for  a  dry  foundation.  The 
evils  resulting  from  the  disrupting  effects  of  water  alternately 
freezing  and  thawing  in  the  foundation  of  a  road  are  apparent 
and  are  well  known.  Freezing  action  not  only  disrupts  a 
road  as  a  whole,  but  its  presence  in  stones  is  promotive  of 
weakness  and  more  rapid  crumbling.  The  presence  of  frost  in 
fragments  of  broken  stone  operates  to  increase  their  brittleness 
to  a  considerable  degree,  and  for  this  reason  gives  rise  to  a  more 
rapid  disintegration  of  the  screenings  and  the  upper  portion 
of  the  road.  In  the  formation  of  ice,  100  volumes  of  water 
expands  to  109  volumes  of  ice,  and  the  pressure  exerted  on 
cooling  the  water  one  degree  below  the  normal  freezing-point 
is  144  tons  per  square  foot.  Its  most  destructive  effect, 
therefore,  is  produced  in  the  structure  of  the  pavement  and 
its  foundation;  if  the  construction  is  defective  and  the  main- 
tenance poor,  water  accumulates  in  the  body  of  the  roadway, 


94  THE  ART  OF  ROADMAKING 

and  on  freezing  either  destroys  the  bond  or  weakens  it  mate- 
rially. 

The  ability  of  water  as  a  medium  of  transportation  of 
material  depends  upon  the  specific  gravity,  the  size  and  the 
form  of  the  fragments,  and  upon  the  velocity  of  the  water,  or, 
what  amounts  to  the  same  thing,  the  grade  of  the  roadbed. 
The  gullying  of  roadbeds  during  heavy  rains  or  melting  snows 
by  washing  particles  of  sand  and  clay  to  the  side  drains 
and  ditches  is  the  most  conspicuous  work  done  by  flowing 
water,  but  the  sorting  process  it  exercises  even  on  gentle 
slopes,  where  the  grains  of  the  least  weight  and  specific  gravity 
are  forced  to  the  surface  of  the  road  to  be  blown  away  by  the 
wind,  is  also  important.  This  sorting  action  arises  from 
the  fact  that  the  sand  grains  will  arrange  themselves  in  water 
in  the  order  of  their  specific  gravities,  the  heaviest  at  the 
bottom. 

The  combined  operation  of  wind  and  water  play  a  con- 
siderable part  in  the  destruction  of  the  roadway.  Measure- 
ments made  by  French  engineers  show  that  about  seven 
cubic  yards  of  material  per  mile  per  annum  are  removed  by 
these  agencies.  Considered  from  the  point  of  view  of  wind 
action  alone,  the  ability  of  wind  to  carry  away  grains  of  any 
rock  depends  on: 

1.  The  form  of  the  particles  subjected  to  the  wind's  influence. 

2.  The  specific  gravity  and  size  of  the  individual  grains. 

3.  The  accessibility  of  the  grains  to  the  action  of  the  wind. 
Heat,  through   changes  of  temperature,  causes   expansions 

and  contractions  which  produce  a  slight  movement  among  the 
component  particles  of  the  material,  thus  breaking  their 
cohesion  and  leaving  them  more  susceptible  to  the  destroying 
effect  of  the  other  agents. 

The  impact  of  falling  rainwater,  while  relatively  unimportant 
as  a  source  of  injury,  causes  a  certain  amount  of  attrition  and 
loosening  of  those  grains  which  it  is  able  to  move  about,  and 
a  certain  breaking  of  the  coherency  of  the  surface  as  far  down 
as  the  water  is  able  to  penetrate. 

Gravity  also  plays  its  part,  as  seen  by  the  work  done  in 
running  water  and  falling  rain,  but  through  its  operation  alone 


MATERIALS  USED  IN  ROAD  CONSTRUCTION  95 

there  is  always  a  tendency  for  grains  and  fragments  of  rock 

to  work  down  the  slopes  towards  the  sides  of  the  road,  which 

may  in  time  completely  destroy  a  roadbed. 
The  mechanical,  or  dynamical,  agencies  are: 
1.  Friction,  resulting  from  the  grinding  action  of 

one  fragment  of  rock  against  another,  due  to  traffic,   Mech*nical 


as, 

a.  Impact  produced  by  the  action  of  horses'  feet. 

b.  Percussive  and  abrading  action  of  moving  wheels. 

c.  Crushing  due  to  the  weight  of  the  load  on  the  wheels. 
2.  The  disrupting  effect  of  roots.. 

The  gradual  destruction  of  a  roadbed  by  the  ordinary 
processes  of  friction  and  impact  is  always  to  be  expected,  and 
if  these  forces  are  applied  in  the  presence  of  water,  thus  pro- 
ducing attrition  in  the  presence  of  a  solvent,  their  destroying 
effects  are  most  energetic. 

The  chemical  agencies  are: 

1.  Decomposition,   shown,  for  example,   by   the 
disintegration  of  the  feldspar-bearing  rocks  whereby      ^  endes 
the  feldspars  and  other  minerals  are  converted  into 

clay,  quartz,  calcite,  etc. 

2.  Solution,  or  the  power  possessed  by  surface  waters  im- 
pregnated with   acids  to  dissolve  most    rocks  and  to  carry 
them  away. 

The  action  of  the  chemical  agencies  is  very  slow,  and  their 
effect  may  be  ignored  except  in  the  case  of  rocks  already  in 
a  state  of  decomposition  or  containing  readily  soluble  mineral 
matter.  The  rocks  that  are  most  susceptible  to  the  solvent 
action  of  water  impregnated  with  acids  are  the  limestones, 
calcareous  sandstones,  and  the  granites  containing  feldspar. 

The  softening  or  partial  decomposition  of  a  road-stone  by 
these  chemical  changes  has  generally  been  regarded  as  a 
destructive  element  in  road  maintenance,  but  although  it 
appears  from  recent  investigations,  that  the  chemical  decom- 
position is  not  so  destructive  as  it  was  formerly  imagined  to 
be,  it  can  hardly  be  doubted  that  the  weathering  properties 
of  a  stone  are  determined  by  resistance  to  chemical  action. 
And  although  this  may  be,  in  some  instances,  slow  and  not 


96  THE  ART  OF  ROADMAKING 

appreciable  on  the  surface  of  a  road  which  is  renewed  from 
time  to  time,  the  internal  structure,  by  the  solvent  action  of 
surface  waters  percolating  through  the  coating  under  abnormal 
conditions  of  weather,  must  be  adversely  affected. 

The  organic  agencies  are  vegetable  or  fungus  growths  that 
thrive  in  damp,  shady  places. 

Organic  ip^    essential  qualities  of  a  good  roadmaking  stone 

agencies. 

may  be  stated  as  follows: 

Paving  Blocks:  Hardness,  toughness,  durability,  uniformity 
of  wear,  retention  of  a  rough  surface  under  traffic  in  all  con- 
ditions of  weather. 

Macadam:    Hardness,   toughness,    durability,   retention    of 

Essential       rough  surface  (though  this  does  not   apply  to  the 

qualities  of    extent  as  in  paving  blocks) ,  and  the  property  of 

roadmaking  binding    necessary    to    maintain    cohesion    under 

varying  conditions. 

These  qualifications  are  rarely  found  together  in  any  high 
degree.  Thus  flint,  though  hard,  is  often  brittle,  and  some 
schistose  or  slaty  rocks,  although  hard  and  tough  when 
quarried,  often  disintegrate  when  exposed  to  the  weather. 
The  quality  of  cohesion  is  rarely  found  in  combination  with 
extreme  hardness  and  toughness.  Material  well  consolidated 
and  united  in  a  mass,  resists  crushing  much  better  than  when 
loose,  and  good  binding  property  enables  a  stone  comparatively 
weak  to  wear  better  than  a  harder  stone  which  does  not  bind. 

Hardness  is  an  essential  quality  and  may  be  described  as 
that  resisting  property  which  a  solid  offers  against  any  dis- 
placement of  its  parts  or  abrasion  of  its  surface. 
iss'  The  definition  adopted  by  the  U.  S.  Road  Material 
Laboratory  is  "the  resistance  which  a  material  offers  to  the 
displacement  of  its  particles  by  friction."  When  applied  to 
materials  used  for  paving  it  signifies  the  resistance  offered  by 
the  material  to  wear  by  abrasion  under  the  action  of  wheels. 

Hardness  varies  inversely  as  the  loss  in  weight  by  grinding 
with  a  standard  abrasive  agent.  A  test  piece  in  the  form  of  a 
cylinder  about  three  inches  in  length  by  one  inch  in  diameter 
is  placed  in  the  grinding  machine  in  such  a  manner  that  the 
base  of  the  cylinder  rests  on  the  upper  surface  of  a  circular 


MATERIALS  USED  IN  ROAD  CONSTRUCTION 


97 


grinding  disk  of  cast  iron,  which  is  rotated  in  a  horizontal 
plane  by  a  crank  movement.  The  specimen  is  weighted  so  as 
to  exert  a  pressure  of  250  grams  per  square  centimeter  against 
the  disk,  which  is  fed  from  a  funnel  with  sand  of  about 
1^  mm.  in  diameter.  After  1000  revolutions  the  loss  in  weight 
of  the  sample  is  determined  and  the  coefficient  of  wear  obtained 
by  deducting  one-third  of  this  loss  from  20. 
Toughness  is  also  essential  quality,  and  is  that  property 


Toughness. 


FIG.  60. — Dorrey  Machine  for  Testing  Hardness. 

which  admits  of  the  constituent  minerals  yielding  to  a  small 
extent  without  separation  of  the  parts,  and  enabling 
the  stone  to  resist  fracture  by  impact.  As  applied 
to  a  paving  material  it  may  be  denned  as  that  property  which 
enables  it  to  resist  fracture  under  the  blows  and  concussions 
produced  by  traffic.  The  determination  of  toughness  is 
obtained  by  the  use  of  a  test  piece  similar  to  that  used  in 
determining  hardness,  and  the  test  is  made  with  an  impact 
machine  constructed  on  the  principle  of  a  pile  driver.  The 


98 


THE  ART  OF  ROADMAKING 


FIG.  61. — Page  Machine 
for  Determining  Toughness. 


FIG.  62. — Page  Impact 
Machine. 


MATERIALS  USED  IN  ROAD  CONSTRUCTION 


99 


blow  is  delivered  by  a  hammer  weighing  2  kg.,  falling  1  cm. 
for  the  first  blow,  which  is  increased  by  1  cm.  for  each  succeed- 
ing blow  until  failure  of  the  test  piece  occurs.  The  number 
of  blows  required  to  cause  this  failure  represents  the  tough- 
ness. 

Durability  depends  on  the  hardness  and  cohesion  of  the 
material,   and    also   on   the   chemical    stability   of   the    con- 
stituent  minerals.     Not   only   is   the   tendency   to 
decompose  present  in  most  stones  when  brought 
under  the  oxidizing  influence  of  air  and  water,  but  nearly  all 
paving  and  road  materials  are  further  subjected  to  the  solvent 
action   of  impure   surface  water,  hence  the   question  of  the 
resistance  of  a  road  material  to  chemical  agents  is,  as  might 
be  supposed,  of  great  importance. 

Percentage  of  wear,  representing  durability,  is  the  amount  of 
material  under  0.16  cm.  in  diameter  lost  by  abrasion  from  a 


FIG.  63. — Deval  Machine  for  Testing  Resistance  to  Abrasion  and 

Impact. 

weighed  quantity  of  rock  fragments  of  definite  size.  The 
rock  sample  is  broken  into  pieces  that  will  pass  through  a 
2.4-inch  ring  but  not  through  a  1.2-inch  ring,  and  after  being 
thoroughly  cleansed,  dried,  and  cooled,  5  kg.  are  weighed  and 
placed  in  a  cast  iron  cylinder  (34  cm.  deep  by  20  cm.  in  diameter) 
closed  at  one  end  and  having  a  tight-fitting  iron  cover  at  the 
other.  This  cylinder  is  one  of  four  attached  to  a  shaft  so  that 
the  axis  of  each  is  inclined  at  an  angle  of  30°  with  that  of 
the  shaft.  These  cylinders  are  revolved  for  five  hours  at  the 
rate  of  2000  revolutions  per  hour,  during  which  the  stone 
fragments  are  thrown  from  one  end  of  the  cylinder  to  the 
other  twice  in  each  revolution.  At  the  end  of  five  hours  the 


100 


THE  ART  OF  ROADMAKING 


machine  is  stopped,  the  cylinders  opened,  and  their  contents 
poured  into  a  basin,  in  which  every  stone  is  carefully  washed  to 
remove  any  adherent  detritus.  This  abraded  material  is 
then  thoroughly  dried,  and  from  the  amount  lost  below  0.16 
cm.  the  per  cent  of  wear  is  estimated. 

The  cementing  value,  or  binding  power,  of  a  road  material, 
is  the  property  possessed  by  a  rock  dust  to  act  as  a  cement 

on  the  coarser  fragments  comprising  crushed  stone 
Cementing    Qr  gravei  roads.     This  property  is  a  very  important 

one  and  is  determined  approximately  as  follows: 
One  kg.  of  the  rock  to  be  tested  is  broken  sufficiently  small  to 


FIG.  64. — Briquette  Machine. 


pass  through  a  6  mm.  but  not  a  1  mm.  screen.  It  is  then 
moistened  with  a  sufficient  amount  of  water  and  placed  in  an 
iron  ball  mill  containing  two  chilled  iron  balls  weighing  25 
pounds  each  and  revolved  at  the  rate  of  2000  revolutions  per 
hour  for  two  hours  and  a  half,  or  until  all  the  material  has  been 
reduced  to  a  thick  dough,  the  particles  of  which  are  not  above 
0.25  mm.  in  diameter.  About  25  grams  of  this  dough  is  then 
piaced  in  a  cylindrical  metal  die,  25  mm.  in  diameter,  and  by 
means  of  a  specially  designed  hydraulic  press,  known  as  a 
briquette  machine,  is  subjected  to  momentary  pressure  of 


MATERIALS  USED  IN  ROAD  CONSTRUCTION  101 

100  kg.  per  square  centimeter.  Five  of  the  resultant  briquettes, 
measuring  exactly  25  mm.  in  height,  are  taken  out  and  allowed 
to  dry  for  12  hours  in  air  and  12  hours  in  a  hot  oven  at  100°  C. 
After  cooling  in  a  desiccator  they  are  tested  by  impact  in  a 
machine  especially  constructed  for  the  purpose.  The  standard 
fall  of  the  hammer  for  a  test  is  1  cm.,  and  the  average  number 
of  blows  required  to  destroy  the  bond  of  cementation  in  the 
five  briquettes  determines  the  cementing  value. 

The  rocks  from  which  stone  for  paving  purposes  is  obtained 
vary  in  quality  within  wide  limits,  according  to  their  geo- 
logical position,  physical  structure,  and  chemical  composition. 
Several  varieties  of  structure  are  met  with  the  same  chemical 
constituents,  this  being  due  to  the  degree  of  crystallization  of 
the  mineral  elements.  These  differences  fit  the  various  rocks 
for  special  purposes. 

The  choice  of  suitable  words  to  describe  the  different  stones 
which  are  used  in  road-building  is  not  an  easy  matter.     When 
petrological  terms  are  used  they  are  often  applied    ciassifica- 
incorrectly,  one  of  the  difficulties  of  this  way  of    tion  of 
naming  stones  being  due  to  the  fact  that  the  dif-    rocks- 
ferent  minerals  forming  the  important  constituents  of  these 
stones   are   combined   in   such   varying  proportions  that  the 
different  kinds  of  stone  shade  into  one  another,  and  many  may 
properly  be  called  by  any  one  of  several  names. 

A  systematic  arrangement  of  rocks  (Table  VII)  has  been 
adopted  by  the  Office  of  Public  Roads  of  the  U.  S.  Department 
of  Agriculture.  This  has  been  made  more  from  the  standpoint 
of  the  road-builder  and  engineer  than  from  that  of  the 
geologist,  although  attention  has  been  given  as  far  as  possible 
to  the  origin  of  the  materials  as  well  as  to  their  mineral  com- 
position. In  this  arrangement  all  rocks  used  as  road  materials 
have  been  separated  into  three  general  groups  or  classes, 
according  to  their  geologic  character,  these  groups  being  again 
divided  into  types  and  families. 


102 


THE  ART  OF  ROADMAKING 


TABLE  VII 
GENERAL  CLASSIFICATION   OF   ROCKS 


GLASS. 


I.  Igneous. 


TYPE. 


FAMILY. 


II.  Sedimentary  . . . 


III.  Metamorphic  ..  . 


f  a.  Granite 

I  6.  Syenite 

1.  Intrusive  (plutonic)  ..  \c,  Diorite 

!  d.  Gabbro 

I  e.  Peridotite 

{a.  Rhyolite 

b.  Trachyte 

i  c.  Andesite 

I  d.  Basalt  and  diabase 

(  a.  Limestone 

1.  Calcareous ^  5.  Dolomite 


2.  Extrusive  (volcanic) 


2.  Siliceous 


1.  Foliated. 


r  a.  Shale 

<j  b.  Sandstone 

(  c.  Chert  (flint) 

r  a.  Gneiss 

.{  b.  Schist 

[  c.  Amphibolite 

a.  Slate 


2.  Non-foliated 


c.  Eclogite 

d.  Marble 


With  the  exception  of  rocks  of  the  second  class,  where 
chemical  distinctions  prevail,  structural  features  indicating 
mode  of  origin  define  the  type,  and  mineral  composition  the 
family.  Photomicrographs,  illustrating  the  structure  and 
mineral  composition  of  the  principal  rocks  are  given  in  Figs. 
65  to  78,  inclusive. 

All  rocks  of  the  igneous  class  are  presumed  to  have  solidified 
from  a  molten  state,  either  upon  reaching  the  earth's  surface  or 
at  varying  depths  beneath  it.  They  vary  in  color 

^rom  the  ^ght  gray'  p*nk)  anc*  brown  of  tne  acid 
granites  and  syenites  to  the  dark  steel  gray  or  black 

of  the  basic  gabbro,  peridotite,  diabase  and  basalt.  The  darker 
varieties  are  commonly  called  "trap."  This  term  is  in  very 
general  use  and  is  derived  from  trappa,  Swedish  for  stair, 
because  rocks  of  this  kind  on  cooling  frequently  break  into 
large  tabular  masses,  rising  one  above  the  other  like  steps. 


rocks"8 


MATERIALS  USED  IN  ROAD  CONSTRUCTION 


103 


The  sedimentary  rocks  as  a  class,   represent   the   consoli- 
dated   products    of    former    rock   disintegration,    as   in   case 


FIG.  65. — Granite. 

of  sandstone,  conglomerate,  shale,  etc.,   or   they  have    been 
formed    from    an    accumulation    of    organic   remains    chiefly 


FIG.  66.— Andesite. 

of    a  calcareous    nature,  as  in   true    limestone  and   dolomite 
(Fig.   72).      Loose  or  unconsolidated    rock   debris  of  a  pre- 


104 


THE  ART  OF  ROADMAKING 


FIG.  69.— Peridotite. 


MATERIALS  USED  IN  ROAD  CONSTRUCTION  105 

vailing  silicious  nature  comprise  the  sands,  gravels,  finer  silts, 
and    clays.     Shell   sands   and   marls,  on  the  other 
hand,  are   mainly  calcareous   and   are   formed   by 
an  accumulation  of  the  marine  shells  and  of  lime- 
secreting  animals. 

Such  terms  as  flagstone,  freestone,  brownstone,  bluestone, 
graystone,  etc.,  are  given  generally  to  sandstones  of  various 
color  and  composition,  while  puddingstone,  conglomerate, 
buccia,  etc.,  apply  to  consolidated  gravels  and  coarse  feldspathic 
sands. 

The  calcareous  rocks  are  of  many  colors,  according  to  the 
amount  and  character  of  the  impurities  present. 

Metamorphic  rocks  are  such  as  have  been  produced  by  the 
prolonged  action  of  physical  and  chemical  forces  (heat,  pressure, 
moisture,  etc.)  on  both  sedimentary  and  igneous 
rocks  alike.  The  foliated  types  (gneiss,  schist,  etc.) 
represent  an  advanced  stage  of  metamorphism  on 
a  large  scale  and  the  peculiar  schistose  or  foliated  structure 
is  due  to  the  more  or  less  parallel  arrangement  of  their 
mineral  components  (Figs.  73,  74,  75).  The  nonfoliated  types 
(quartzite,  marble,  slate,  etc.)  have  resulted  from  the  altera- 
tion of  sedimentary  rocks  without  materially  affecting  the 
structure  and  chemical  composition  of  the  original  material. 
(Fig.  78). 

The  color  of  metamorphic  rocks  varies  between  gray  and 
white  of  the  purer  marbles  and  quartzites  to  dark  gray  and 
green  of  the  gneisses,  schists,  and  amphibolites.  The  green 
varieties  are  commonly  known  as  greenstones  or  greenstone 
schists. 

The  family   groups  given   in    Table  VII  may  be    further 
subdivided   into   many   subfamilies    or    varieties — 
as,  for  instance,  biotite-granite,  hornblende-schist,  Primary 
etc.,  according   to   characteristic   primary   mineral  constituents<, 
constituents,   a   list   of   which    is   given    in   Table 
VIII,   together    with    their    approximate    chemical    composi- 
tion. 


106 


THE  ART  OF  ROADMAKING 


FIG.  70.— Rhyolite. 


FIG.  71. — Diabase  (Trap). 


FIG.  72.— Crystalline  Limestone. 


MATERIALS  USED  IN  ROAD  CONSTRUCTION 


107 


TABLE  VIII 

PRIMARY  MINERAL  CONSTITUENTS  OF  ROCKS 
USED  FOR  ROADMAKING" 


NAME. 

Quartz 

Orthoclase  (micro- 

cline) 

Plagioclase 

Augite 

Hornblende. ...... 

Calcite 

Dolomite 

Biotite 

Muscovite 

Magnetite 

Rock  glass 

Garnet 

Olivine 

Pyrite 

Hematite 

Hypersthene  .... 

Titanite 

Apatite 

Zircon  .  . 


CHEMICAL  COMPOSITION. 


Silica 


Silicate  of  alumina  and  potash 

Silicate  of  alumina,  lime,  and  soda 

Silicate  of  lime,  magnesia,  iron,  and  alumina 

Silicate  of  lime,  magnesia,  iron,  and  alumina 

Carbonate  of  lime 

Carbonate  of  lime  and  magnesia 

Hydrous  silicate  of  alumina,  iron,  magnesia,  and  potash 

Hydrous  silicate  of  alumina  and  potash 

Magnetic  oxide  of  iron 

Variable 

Silicate  of  iron,  alumina,  and  lime 

Silicate  of  magnesia  and  iron 

Disulphide  of  iron 

Oxide  of  iron 

Siliacte  of  iron  and  magnesia 

Titano-silicate  of  lime 

Phosphate  of  lime 

Silicate  of  zirconia 


The  physical  properties  of  the  principal  road-making  rocks 
are  given  in  Table   IX,  in  which  they  are  arranged      Physical 
according    to    the    classification    given    in    Table      properties 
VII,  with  their  more  important  varieties.  of  rocks. 

TABLE  IX 
PHYSICAL   PROPERTIES   OF   ROCKS   FOR   ROADMAKING  * 


Physical  Properties. 


Rock  Varieties. 

Per  Cent 
Wear.1 

Tough- 
ness.1 

Hardness.1 

Cement- 
ing Value.1 

Specific 
Gravity.2 

Granite 

3  5 

15 

18    1 

20 

2  65 

Biotite  granite  
Hornblende  granite.  .... 
Augite  syenite  
Diorite 

4.4 
2.6 
2.6 
2  9 

10 
21 
10 
21 

16.8 

18.3 
18.4 
18  1 

17 
30 
24 
41 

2.64 
2.76 
2.80 
2  90 

Augite  diorite  

2.8 

19 

17.7 

55 

2  98 

Gabbro 

2  8 

16 

17  9 

29 

3  00 

Peridotite  

4.0 

12 

15.2 

28 

3.40 

(Table  IX  continued  on  p.  109.) 


108 


THE  ART  OF  ROADMAEJNG 


FIG.  75. — Mica-schist. 


MATERIALS  USED   IN  ROAD  CONSTRUCTION 
TABLE   IX* — Continued. 


109 


Rock  Varieties. 

Physical  Properties. 

Per  Cent 
Wear.1 

Tough- 
ness * 

Hardness.  ijngevllue".i 

Specific 
Gravity.2 

Rhyolite 

3.7 
4.7 
3.3 
5.3 
2.0 
2.5 

5.6 
5.7 
6.9 
3.3 
7.4 
10.8 

3.8 
3.7 
3.2 
4.4 
4.0 
4.2 
3.7 
2.9 

4.7 
2.9 
3.2 
2.3 
2.4 
3.6 

20 

11 

23 
17 
30 
24 

10 
10 
26 
17 
15 
15 

12 
10 
19 
10 

21 
10 

12 
19 
17 

27 
31 
16 

17.8 
13.7 
17.1 
15.6 
18.2 
17.5 

12.7 
14.8 
17.4 
15.3 

8.3 
19.4 

17.7 
17.1 
17.5 
17.3 

16.5 
19.0 

11.5 
18.4 
18.3 
18.6 
17.4 
16.0 

48 
189 
111 
239 
49 
156 

60 
42 
90 
119 
60 
27 

26 
30 
41 
30 
16 
24 
53 
29 

102 
17 
21 
17 
21 
47 

2.60 
2.50 
2.90 
2.75 
3.00 
2.95 

2.70 
2.70 
2.55 
2.70 
2.66 
2.50 

2.68 
3.02 
2.76 
2.80 
2.70 
2.90 
3.00 
3.00 

2.80 
2.70 
2.70 
3.00 
3.30 
3.03 

Anclesite  
Fresh  basalt 

Altered  basalt  

Fresh  diabase 

Altered  diabase  
Limestone  

Dolomite 

Sandstone                

Feldspathic  sandstone.  .  . 
Calcareous  sandstone  .  .  . 
Chert 

Granite  gneiss  

Hornblende  gneiss     .  . 

Biotite  gneiss  

Mica  schist 

Biotite  schist  

Chlorite  schist 

Hornblende  schist 

Amphibolite  
Slate       

Quartzite 

Feldspathic  quartzite  .  .  . 
Pyroxene  quartzite  
Eclogite  

Epidosite 

*  Condensed  from  an  extensive  table  of  the  mineral  composition  of 
rocks  compiled  by  the  Bureau  of  Chemistry  of  the  U.  S.  Dept.  of  Agri- 
culture. 

1 .  The  tests  for  obtaining  these  values  were    outlined  in  pages   97- 
100. 

2.  The  specific  gravity  is  the  weight  of  the  material  compared  with  that 
of  an  equal  volume  of  water,  and  is  obtained  by  dividing  the  weight  in 
air  of  a  rock  fragment  by  the  difference  of  its  weight  in  air  and  water. 
Given  the  specific  gravity,  the  weight  per  cubic  foot  of  a  rock  is  found 
by  multiplying  this  value  by  62.5  pounds,  the  weight  of  a  cubic  foot 
of  water. 


THE  ART  OF  ROADMAKING 


FIG.  78. — Quartzite. 


MATERIALS  USED  IN  ROAD  CONSTRUCTION  111 

From  the  results  of  the  extensive  series  of  tests  of  road 
materials  made  by  various  methods  by  the  Office  of  Public 
Roads,  the  following  conclusions  have  been  reached  :*  c  . 

1.  Igneous  and  metamorphic  rocks,  owing  to  a  regarding 
higher    degree    of    crystallization    and    a    prepon-  paving 
derance  of  silicate  minerals,  offer  a  greater  resistance  S1 

to  abrasion  than  nearly  all  varieties  of  sedimentary  rocks. 

2.  The  coarse-grained  intrusive  rocks  of  the  igneous  class 
are  harder,  but  break  more  readily  under  impact  than  the 
finer-grained  volcanic  varieties  of  like  mineral  composition. 

3.  The  deleterious  effect  of  atmospheric  weathering  on  the 
wearing  qualities  of  rocks  has  been  demonstrated. 

4.  The   cementing  value  of  rocks  is,  to  a  certain  degree, 
measured  by  the  abundance  of  secondary  minerals  resulting 
from  rock  decay. 

5.  Metamorphic  rocks  have,  as  a  rule,  a  low  binding  power, 
owing  to   a  regeneration  of  secondary  minerals  and  to  the 
effects  of  heat  and  pressure.     The  foliated  types  part  readily 
along  planes  of  schistosity,  and  therefore  are  not  well  adapted 
to  road  construction. 

6.  The  quantitative  mineral  analysis  of  rocks  serves  to  a 
certain  extent  as  a  measure  of  their  useful  properties  for  road 
construction. 

The  principal  varieties  of  rock  employed  for  paving-blocks 
are  the  granites,  basalts,  sandstones,  and  limestones,  because 
of    the    facility    with    which    they    split    into    the  Princi  al 
desired    shapes;     for    broken-stone    pavements    all  varieties  of 
varieties    of    rock    are    used,    including    the    flints  roadmaking 
and  gravels. 

Granite  is  an  unstratified  igneous  rock,  consisting  of  quartz, 
feldspar,  and  some  form  of  mica,  or  hornblende,  in  addition 

to  which  essential  constituents  one  or  more  acces- 

Granite, 
sory  minerals  may  be  present.     The  character  of 

the   granite   is   determined   principally   by  its   essentials,  but 
the  accessories  have  much  to  do  with  its  qualities. 


*  U.  S.  Department  of  Agriculture,  Office  of  Public  Roads,   Bulletin 
No.  31. 


112  THE  ART  OF  ROADMAKING 

The  colors  of  granite  are  white,  gray,  various  shades  of  red, 
and  green,  the  color  being  generally  fixed  by  the  feldspar,  but 
the  mica  is  often  a  governing  characteristic,  the  presence  of 
muscovite  (potash  mica) ,  making  a  granite  light,  while  biotite 
(iron-magnesia  mica)  has  the  opposite  effect. 

The  durability  of  granite  depends  to  a  great  extent  upon  the 
character  of  the  feldspar  present,  too  much  of  it  rendering  the 
granite  soft  and  tough,  but  liable  to  decomposition,  while  a 
large  amount  of  quartz  will  make  it  hard  and  brittle.  The 
susceptibility  to  polish  and  its  ability  to  resist  the  action  of 
the  elements  depend  greatly  upon  the  accessory  components; 
hornblende  permits  it  to  take  a  high  polish,  while  pyroxene, 
being  very  brittle,  often  gives  a  pitted  appearance  to  an  other- 
wise smooth  surface. 

The  structure  of  granite  varies  considerably  from  coarse  to 
fine  and  is  termed  the  holocrystalline,  which  implies  that  it  is 
made  up  exclusively  of  crystalline  particles  having  clear,  well- 
defined  boundaries.  A  fine-grained  stone,  of  small  and  evenly 
distributed  grains,  is  compact  in  texture,  excluding  air  and 
moisture,  both  of  which  are  destructive  agencies  to  all  minerals, 
and  may  be  more  easily  cut  and  polished  than  a  coarse-grained 
stone.  On  account  of  its  peculiar  structure,  granite  can 
easily  be  broken  into  blocks  of  any  desired  shape  or  size.  It 
is  specially  adapted  in  roadwork  for  paving  blocks,  curbing, 
flagging,  basin-heads,  crossing  stones,  and  gutter  stones;  it  is 
also  crushed  and  used  for  manufacture  of  concrete  and  arti- 
ficial stone. 

The  term  "granite,"  which  should  in  a  strict  sense  not  be 
applied  to  any  stone  not  containing  mica,  is  often  applied 
commercially  and  popularly  to  what  are  known  as  the  gneisses 
(foliated  and  bedded  granites),  syenite,  diorite,  gabbro,  and 
other  crystalline  rocks  whose  uses  are  similar. 

Syenite  (so  named  because  it  was  first  found  in  Syene, 
Egypt)  consists  of  feldspar  and  hornblende,  with  or  without 
quartz.  It  is  massive  and  furnishes  excellent  material  for 
paving  blocks,  but  is  seldom  found  or  used  in  this  country. 

Diorite  is  composed  of  a  crystalline  mixture  of  oligoclase 
(soda  and  lime  feldspar)  and  hornblende  with  magnetic  iron 


MATERIALS  USED  IN  ROAD  CONSTRUCTION  113 

and  apatite,  and  occurs  under  conditions  similar  to  syenite. 
When  the  component  minerals  are  fine-grained  and  compact 
they  make  a  very  satisfactory  material  for  broken-stone  roads. 

Basalt  is  one  of  the  names  given  to  a  large  group  of  un- 
stratified  eruptive  rocks,  commonly  called  trap-rock  (See 
page  102).  The  trap-rocks  are  generally  close- 
grained  and  compact  in  texture;  they  are  hard 
and  tough  and  break  irregularly  and  are  usually  difficult  to 
work.  In  color  they  are  dark  gray,  dark  green,  or  grayish 
black,  the  dark  color  being  due  to  a  larger  proportion  of 
magnetite,  which  also  contributes  to  the  high  specific  gravity 
of  these  rocks.  The  trap-rock  of  the  Palisades  on  the  west 
shore  of  the  Hudson  river  split  easily  into  blocks,  and  has 
been  extensively  and  satisfactorily  used  for  paving  in  the 
cities  of  New  York  and  New  Jersey. 

Sandstone  is  formed  by  the  decomposition  on  disintegra- 
tion of  rocks.     The  pockets  of  sand  often  found  in  beds  of 
earth  or  limestone  are  the  results  of  boulders  being 
surrounded  when  these  deposits  of  clay  or  stone 
were  first  made,  and  which  long  afterwards  decayed,  leaving 
in   their   places   these   pockets   of   sand,    whose    composition 
depends  upon  the  minerals  contained  in  the  original  rocks. 

Sandstone  is  formed  by  grains  of  sand  being  deposited  in 
beds  by  some  agency  and  afterwards  compacted.  The  sand 
proper  is  almost  all  quartz,  as  this  mineral  is  indestructible 
from  the  ordinary  action  of  the  elements,  while  the  cementing 
portion  of  the  original  rock  has  generally  been  decomposed 
and  a  new  substance  formed.  The  solidification  of  the  stone 
is  caused  by  great  pressure,  partial  solution,  fusion  of  some 
of  its  own  parts,  or  by  the  infiltration  of  some  cementing 
material,  such  as  silica  lime,  or  the  oxides  of  iron.  It  is 
generally  found  in  layers  of  variable  thickness  separated  from 
each  other  by  some  softer  material,  the  thickness  of  these  layers 
probably  depending  upon  the  time  one  force  acted  continu- 
ously upon  the  sand,  the  softer  deposits  being  made  during  the 
intervening  period. 

The  texture  of  the  stone  varies  according  to  the  sizes  of  the 
sand  grains. 


114  THE  ART  OF  ROADMAKING 

Sandstones  are  of  many  colors,  the  most  common,  however, 
being  gray,  yellow,  and  red.  These  colors  are  determined  by 
the  different  combinations  of  iron;  the  red  being  due  to 
peroxides,  and  the  yellow  to  hydrous  peroxides.  Some 
varieties  will  change  color  upon  exposure  to  the  air  or  the 
application  to  heat,  on  account  of  the  oxidation  of  the  iron. 

In  street  construction  sandstones  are  used  for  curbing, 
cross-walks,  flagging  and  for  paving  the  roadway. 

Limestone,    like    sandstone,    is    a    sedimentary    rock,    but 
differs  from  it  very  much  in  its  formation. 

Water  flowing  down  from  a  rough  mountainous 
country  carries  with  it  a  large  amount  of  matter  both  in  solu- 
tion and  in  suspension.  As  the  stream  reaches  any  larger 
body  of  still  water  its  velocity  gradually  decreases  and  that 
portion  is  suspension  is  deposited,  the  coarser  and  heavier 
near  the  shore  and  the  finer  farther  out.  Calcareous  matter, 
as  a  rule,  being  soft,  is  generally  fine,  and  is  borne  from  a 
distance  and  finally  deposited  as  silt. 

All  these  flowing  streams  contain  a  considerable  quantity  of 
lime  in  solution  which,  being  in  part  precipitated,  serves  to 
consolidate  the  silt.  From  this  same  source  certain  marine 
animals  derive  their  supply  for  their  shells.  Upon  the  death 
and  decomposition  of  the  animal  life  the  shells  and  corals  are 
left  and,  breaking  up,  in  time  form  calcareous  banks  which 
later  on  become  beds  of  limestones  of  more  or  less  fragmental 
nature. 

These  formations  are  generally  in  well-defined  beds  nearly 
level  when  not  disturbed  by  any  subsequent  force,  but  when 
they  have  been  acted  upon  by  some  of  the  forces  so  frequent 
during  the  formation  of  the  earth's  crust,  the  strata  are  found 
at  all  angles  with  the  horizontal. 

Limestones  differ  greatly  in  structure,  from  the  variety 
highly  charged  with  fossils  to  the  hard  compact  rocks  denser 
and  heavier  than  granite.  They  also  vary  in  color  according 
to  the  iron  and  carbonaceous  compounds  that  may  be  present. 

Silica  and  clay  are  often  found  in  composition,  and  when 
they  exist  in  quantities  exceeding  ten  per  cent  the  stone  is 
said  to  be  "  hydraulic."  That  is,  upon  being  burned  and  ground 


MATERIALS  USED  IN  ROAD  CONSTRUCTION  115 

it  can  be  made  into  mortar  that  will  harden  under  water,  a 
property  not  belonging  to  ordinary  limestones. 

Marble  is  a  crystalline  limestone  of  such  a  character  as  to 
be  capable  of  receiving  a  high  polish. 

Of  the  other  materials  used  in  road  making,  wood  is  treated 
in  Chapter  XVI;  asphalt,  in  Chapter  XVII,  and  concrete  in 
Chapter  XVIII. 

Sand  is  an  aggregation  of  loose  incoherent  grains,  crystal- 
line in  structure  and  angular  in  shape,  of  silicious,  argillaceous, 
calcareous,  or  other  material,  derived  from  the 


disintegration   of   rocks   or   other   mineral   matter,          n   and 


and  unmixed  with  earth  or  organic  matter. 

Clay  consists  of  a  hydrated  silicate  of  alumina  in  combina- 
tion with  other  substances  derived  from  the  feldspathic  rocks, 
which  by  their  disintegration  and  decomposition  have  formed 
the  clay.  Pure  clay  is  soft,  white  and  opaque;  has  a  char- 
acteristic odor,  is  infusible,  and  insoluble  either  by  water, 
nitric  or  hydrochloric  acids.  It  may  be  converted  by  water 
into  a  doughy,  tenacious,  plastic  paste;  it  absorbs  water, 
but  when  burned  at  a  sufficiently  high  temperature  it  becomes 
hard  and  gritty,  and  loses  almost  wholly  this  property  of 
combining  with  water. 

With  the  single  exception  of  ordinary  earth  or  loam,  sand 
and  clay  in  combination  form  probably  the  lowest  type  of 
material  available  for  road  purposes. 

Sand  of  itself,  while  at  its  best  in  winter  and  spring,  does 
not  ever  have  sufficient  stability  to  sustain  traffic  over  it, 
and  clay,  of  itself,  is  open  to  the  same  or  greater  objection 
than  loam.  It  is  possible,  however,  to  combine  sand  with 
clay  in  such  a  manner  that  under  moderate  traffic  and  favorable 
climatic  conditions  a  fairly  serviceable  road  may  be  obtained. 
(See  Chapter  VII.) 

The  principal  use  of  sand  is  as  a  foundation  for  broken  stone, 
a  cushion  and  bed  for  stone  paving-blocks,  and  as  a  joint 
filling.  For  these  purposes  it  is  most  suitable,  because  when 
confined  so  that  it  cannot  escape  or  spread,  it  possesses  the 
valuable  property  of  incompressibility,  and  mobility,  or  the 


116  THE  ART  OF  ROADMAKING 

property  of  assuming  a  new  position  when  any  portion  of 
it  is  disturbed. 

Sharp  sand,  with  angular  grains,  is  much  better  than  sand 
with  rounded  grains,  although  it  is  often  difficult  to  obtain. 
The  sharpness  of  sand  can  be  determined  by  rubbing  a  few 
grains  in  the  hand  or  by  crushing  it  near  the  ear  and  noting 
if  a  grating  sound  is  produced. 

The  sand  for  bedding  rocks  and  for  jointing  should  be  free 
from  loam  or  clay.  The  clearness  may  be  tested  by  rubbing 
a  little  of  the  dry  sand  in  the  palm  of  the  hand  and,  after 
throwing  it  out,  noticing  the  amount  of  dust  left  in  the  hand. 
The  cleanness  of  sand  may  also  be  judged  by  pressing  it  to- 
gether between  the  fingers  while  it  is  damp;  if  the  sand  is 
clean,  it  will  not  stick  together,  but  will  immediately  fall 
apart  when  the  pressure  is  removed. 

Gravel  is  an  accumulation  of  fragments  of  stone,  or  small 

stones,  varying  in  size  from  a  pea  up  to  an  egg.     It  is  often 

intermixed   with   other  substances,   such   as   sand, 

clay,   loam,   etc.,   from   each   of  which   it   derives 

a  distinctive  name. 

As  a  rule,  gravel  is  unserviceable  for  roadmaking,  mainly 
due  to  the  smoothness  of  the  surface  of  the  pebbles,  preventing 
their  binding  together  in  the  manner  of  broken  stone.  There 
is  also  an  absence  of  dust  or  other  cementing  material,  and  even 
if  such  binder  is  furnished  it  is  difficult  to  effectively  hold  the 
rounded  and  polished  surfaces  of  the  pebbles  together. 

At  the  present  time  there  should  be  no  difficulty  in  de- 
termining the  relative  values  of  stones  for  road 
purposes  in  any  locality.  The  Office  of  Public 

ment  tests.  R°ads,  of  the  United  States  Department  of  Agri- 
culture, undertakes  to  make  tests  and  analyses  of 

samples  of  stones,  without  charge,  and  to  give  advice  as  to 

their  value  for   roadbuilding  purposes. 


CHAPTER   VII 

EARTH,   GRAVEL,   SAND   AND   CLAY  ROADS 
EARTH  ROADS 

THE  term  "Earth  Roads"  includes  all  those  constructed  of 
natural  soil,  whether  loam,  clay  or  sand,  without  a  crust  or 
other  road  covering.  The  earth  road  is  the  cheapest  form 
of  road  as  regards  first  cost,  and  is  generally  the  pioneer  in 
any  new  country.  In  its  simplest  form  it  consists  of  dirt 
from  the  sides,  simply  thrown  up  into  the  center,  with  little 
or  no  regard  for  the  formation  of  a  crown  for  the  lateral 
shedding  of  rain-water.  The  bulk  of  the  country  roads  of 
America  are  made  of  earth  alone,  and  as  a  well-made  earth 
road  forms  an  excellent  foundation  for  a  graveled  or  a  broken- 
stone  road,  and  its  construction  is  in  many  cases  preparatory 
to  a  more  permanent  improvement,  the  importance  of  scien- 
tific design  and  construction  will  be  easily  seen. 


FIG.  79. — Earth  Road  With  Flat  Surface,  as  ordinarily  constructed. 

If,  as  is  often  done,  the  loose  earth  be  thrown  into  the 
middle  of  the  road  to  be  compacted  by  the  wheels  of  the  traffic, 
the  action  of  the  wheels  will  be  to  cut  it,  or  at  least  to  pack 
it  in  a  very  uneven  manner,  producing  a  surface  uneven  and 
full  of  ruts,  which  will  hold  water  and  ultimately  cause  the 
destruction  of  the  road.  In  case,  however,  the  surface  be 
properly  rolled,  it  may  usually  be  made  sufficiently  firm  to 
hold  up  the  wheels  and  retain  its  form  under  the  traffic,  and 
if  kept  free  from  ruts  until  thoroughly  compacted  will  thus 
be  rendered  much  more  capable  of  resisting  the  penetration 
of  water  and  shedding  it  into  the  side  gutters. 

117 


118 


THE  ART  OF  ROADMAKING 


The  first  step  in  the  construction  of  a  new  earth  road  in 

most  localities  is  to  clear  the  surface  over  the  entire  width 

of  all  stumps,  brush,  vegetable  matter,  rocks,  and 

The  first        boulders.     These    should    be    removed     and    the 

step  m  con-  regu^jn~   holes   filled    in   with    suitable    materials 
strucuon. 

thoroughly    tamped    or    rolled,    before    the    road 

embankment  is  commenced.     No  perishable  material  should 
be  used  in  forming  the  permanent  embankment. 


FIG.  80. — Proper  Cross-section  for  Road  in  Loamy  Soil.     Crown  1  inch 

per  foot. 


FIG.  81. — Proper  Cross-section  for  a  Clay  Road.     Crown  1J  inches  per 

foot. 


FIG.  82.  —  Cross-section  of  Road  as  usually  left  by  the  grader,  with  the 
last  cut  of  the  blade  at  2.  It  should  have  been  left  as  in  Fig.  81, 
with  the  last  cut  of  the  grader  blade  in  position  1. 


-No  Travel  .....  —^.-Travel  —  •>> 


FIG.  83.— Cross-section  of  Road  Graded  Too  Wide,  with  a  pile  of  loose 
dirt  and  sods  in  the  center.  The  travel  naturally  takes  the  sides 
where  the  earth  has  been  scraped  off  by  the  grader. 

In  a  wet  district  or  where  the  soil  is  naturally  damp  the 
trees  and  scrub  should  be  cleared  the  full  width  of  the  right- 
of-way  to  allow  of  proper  evaporation,  but  in  hot  and  dry 
districts,  where  the  comfort  of  travelers  must  be  considered, 
it  is  well  to  leave  growing  trees  on  each  side  of  the  roadway. 

Whenever  the  subgrade  soil  is  found  unsuitable  it  should 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS  119 

be  removed  and  replaced  with  good  material  rolled  to  a 
bearing.  The  roadbed  having  been  brought  to  the 

required  grade  and  crown,  should  be  rolled  several  P5epar?tljn 
x.  '  i.  '  11  •  v  •  of  roadbed, 

times  to  compact  the   suriace  and  all  inequalities 

leveled  up  and  re-rolled.  On  this  prepared  subgrade  the 
earth  should  be  spread,  harrowed,  if  necessary,  and  then 
rolled  to  a  bearing  by  passing  the  road  roller  a  number  of 
times  over  every  portion  of  the  surface. 

In  level  countries  and  with  narrow  roads   enough  material 
can  generally  be  excavated  in  forming  the  side  ditches  to  raise 
the  roadway  above  the  subgrade.     If  not,  the  re- 
quired  earth   may   be   obtained   by   widening   the  Preparation 
side   excavations,    or    from    cuttings    on    the   line  surface 
of   the   new   roadway,    or   from   borrow-pits   close 
by.     When  the  earth  is  brought  up  to  the  final  height  it  is 
again  harrowed,  then  trimmed  by  means  of  road  levelers  or 
road  machines,  and  ultimately  rolled  to  a  smooth  and  solid 
surface,   the   cross-section  of  the  roadway  being  maintained 
during  the  last  rolling  stage  by  the  addition  of  earth  as  needed. 
Before  the  earth  road  is  opened  to  traffic,  the  side  ditches 
should  be  cleaned  and  left  with  the  drain  tiling  in  good  working 
order. 

On  account  of  the  loose  character  of  the  material,  earth 
roads  require  most  careful  design  in  order  that  the  road  may 
be  kept  dry.  Water  is  the  great  destroyer  of  earth 
roads,  and  drainage  is  especially  important  in  their 
proper  making  and  maintenance  because  the  material  of  the 
roadway  is  more  susceptible  to  the  action  of  the  water  and 
more  easily  destroyed  than  any  other  material  used  in  the 
construction  of  roads.  If  not  properly  drained  the  rain  and 
snow  soften  it  and  it  soon  becomes  impassable  mud.  If,  on 
the  other  hand,  water  is  allowed  to  run  on  the  road  surface, 
it  will  soon  wash  away  the  earth  and  form  gullies. 

As  stated  in  Chapter  V,  the  prime  necessity  of  every  road  is 
thorough  drainage;  without  it,  the  road  cannot  long  remain 
intact.  In  the  construction  of  earth  roads  it  is,  in  fact,  the 
most  important  matter  to  be  considered;  drainage  alone  will 
often  change  a  bad  earth  road  to  a  good  one,  and  the  best 


120  THE  ART  OF  ROADMAKING 

road  may  be  quickly  destroyed  by  the  absence  of  proper 
drainage. 

Side  ditches  are  provided  for  country  roads  in  most  cases; 
but  these  are  often  imperfectly  made,  and  even  the  best 
side  drains  are  usually  inadequate  to  relieve  the  road  from 
its  soggy,  impassable  condition.  Nothing  brings  relief  except 
the  slow  process  of  evaporation,  and  even  when  a  road  is 
dried  by  the  sun  and  wind  it  is  generally  left  in  a  rough, 
rutty  condition. 

With  wet  or  clayey  roadways  surface  drainage  alone 
is  not  sufficient.  Without  underdrainage  the  crown  of  such 
roadways  will  dry  only  by  the  action  of  the  sun,  during  which 
time  the  topping  becomes  more  and  more  rutted  by  the  passing 
traffic.  A  subdrain  in  such  soils  will  not  prove  efficient  for 
more  than  about  12  feet  on  each  side;  hence,  two  lines  of 
longitudinal  subdrains  are  needed  on  those  roads  that  pass 
through  wet  places,  low-lying  lands,  or  clayey  soils.  They 
should  have  an  average  fall  of  about  1  in  100,  with  a  minimum 
of  1  in  1000.  At  short  intervals  of  about  36  to  100  feet 
apart,  are  placed  cross  drains  to  discharge  the  water  into  the 
side  ditches,  which  may  have  a  fall  up  to  1  in  30.  It  is 
advantageous  to  bed  these  tiles  in  well-rammed  brick  frag- 
ments and  to  cover  them  with  stone,  taking  care  that  nothing 
interferes  with  their  free  discharge.  The  bottom  of  the  tiles 
should  be  laid  both  to  the  proper  grade  and  below  the  frost 
line,  after  which  the  tile  trench  is  filled  up  to  subgrade  with 
clean  gravel,  small  stones,  or  broken  stone  or  bricks.  The 
cross  drains  should  be  made  of  unglazed  tiles,  with  outlet 
sections  of  vitrified  culvert  pipes.  Regular  branch  pipes 
should  connect  the  longitudinal  and  cross  tiles.  On  level 
reaches  the  lateral  roadway  slopes  for  surface  drainage  should 
not  be  less  than  1  in  24,  and  side  ditches  should  be  provided, 
when  necessary.  A  rapid  discharge  of  the  side  ditches  is  of  the 
utmost  importance  to  roadway  preservation. 

Too  many  trees  should  not  be  allowed  on  the  sides  of  dirt 
roads,  because  they  impede  the  drying  action  of  the  sun  and 
wind,  and  their  water-seeking  roots  are  apt  to  creep  into 
the  drains  and  thus  obstruct  or  prevent  the  junction  of  the  tiles. 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS      121 

The  water  having  been  taken  from  under  the  road  and  off 
the  road  it  is  next  necessary  to  carry  it  across  and  away  from 
the  road  by  proper  culverts.     These  should  be  put 
in  at  every  point  that  water  can  be  carried  away 
from  the  road  by  natural  channels,  and  their  location  will  be 
regulated  by  the  position  of  these  channels.     Probably  in  no 
way  is  more  money  wasted  in  road  work  than  in  the  building 
of    cheap    and    temporary    culverts.     Nothing   but    the    best 
should  be  built  even  if  something  else  must  be  sacrificed. 
(See  Chapter  V.) 

The  great  point  in  having  good  roads  is  the  care  of  them 
after  they  are  made.     It  is  absolutely  necessary  in  order  to 
have  good  roads  that    it   must    be    the   constant 
duty  of  someone  to  look  after  them  after  the  road      a*n  ena.nce 
is  built,  especially  during   and    following    a    rain, 
that  water  may  be  kept  off  as  far  as  possible. 

Dirt  roads  are  readily  repaired  by  a  judicious  use  of  road 
machines  and  road  rollers.  Ploughs  and  scoop  scrapers  should 
should  not  be  used  for  this  purpose,  as  they  would  loosen  the 
portion  of  the  road  that  was  already  consolidated  by  the 
traffic.  Repairs  should  be  attended  to,  particularly  in  the 
spring  of  the  year,  and  whenever  the  roadway  becomes  rutted. 

Any  small  breaks  in  the  surface  must  be  immediately 
repaired  and  ruts  filled  and  smoothed  before  they  become 
serious. 

The  work  required  to  keep  a  road  in  repair  depends  upon 
the  nature  of  the  surface  and  the  efficiency  of  the  drainage. 
A  well-constructed  road  of  good  material  will  be  much  easier 
and  less  expensive  to  keep  in  repair  than  one  in  which  the 
surface  is  not  firm  enough  to  resist  the  cutting  action  of  the 
traffic,  or  which  has  a  surface  of  material  readily  softened  by 
the  action  of  water  which  may  fall  upon  it. 

Earth  roads  under  the  most  favorable  conditions  are  expen- 
sive to  maintain,  and  especially  so  under  the  common  system 
of  repairing  once  or  twice  a  year,  or  at  long  intervals.  This 
system  is  not  only  costly  in  the  work  required,  which  usually 
amounts  to  a  practical  reconstruction  of  the  road  each  time 
repairs  are  undertaken,  but  it  is  ineffectual  in  that  the  road 


122  THE  ART  OF  ROADMAKING 

for  the  larger  portion  of  the  time  is  out  of  repair  and  in  bad 
condition,  even  if  the  work  of  construction  has  been  well 
done,  which  is  not  usually  the  case  where  this  method  obtains. 

The  only  way  to  keep  an  earth  road  in  good  condition  is 
by  the  employment  of  men  whose  business  it  shall  be  to  con- 
tinually watch  the  road,  and  make  such  small  repairs  as  may 
be  necessary  from  time  to  time.  The  small  washes  that  may 
occur  during  heavy  storms,  ruts  formed  by  wagons  traveling 
in  the  same  tracks,  or  in  passing  over  soft  spots  when  the 
road  is  wet,  or  any  small  breaks  in  the  surface  of  the  road, 
should  be  at  once  attended  to  and  carefully  filled  with  new 
material. 

When  there  are  long-continued  rains,  or  when  the  ice  and 
snow  of  winter  are  melting  in  the  spring,  an  earth-road  surface 
will  necessarily  be  more  or  less  softened  and  cut  by  passing 
vehicles;  and  at  such  time  a  road  of  this  character  cannot  be 
maintained  in  the  same  condition  as  in  dry  weather,  or  in  the 
condition  which  would  be  possible  with  a  less  permeable 
surface,  but  if  at  the  beginning  of  the  wet  period  it  be  in 
proper  form  and  if  the  drainage  be  efficient,  the  injury  to  the 
road,  as  well  as  the  duration  of  the  bad  condition,  will  be 
reduced  to  a  minimum.  As  soon  as  possible  after  such  a  wet 
period,  the  roads  should  be  gone  over  with  the  scraper,  or  a 
"  split-log  drag."  This  should  be  done  before  the  ground 
becomes  thoroughly  hard  and  dry,  as  it  will  work  more  freely, 
and  may  be  compacted  much  closer  than  afterward. 

The  difficulty  in  the  cost  of  maintaining  the  road  will  of 
course  vary  with  the  nature  of  the  traffic  that  passes  over  it. 
A  road  for  light  driving  will  be  much  easier  to  keep  in  repair 
than  one  used  for  heavy  loads,  and  as  the  amount  of  heavy 
traffic  becomes  greater,  the  economy  of  the  earth  surface  is 
lessened,  and  the  desirability  of  the  substitution  of  a  more 
durable  wearing  surface  increases. 

The  width  of  the  wheel  tires  upon  which  the  loads  are 
carried  is  also  important  in  its  effect  upon  the  cost  of  keeping 
a  road  in  repair.  Narrow  tires  cut  and  rut  the  surface  of  a 
road,  while  those  of  sufficient  width  act  as  rollers  to  compact 
the  material. 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS  123 


GRAVEL  ROADS 

Gravel  furnishes  a  very  acceptable  substitute  for  stone  as  a 
material  for  the  construction  of  roads  with  a  moderate 
amount  of  travel,  and,  when  well  constructed,  a  gravel 
road  is  a  satisfactory  one.  It  has  to  commend  it  its  ease 
of  laying  and  ease  of  repair,  but  it  has  not  the  durable 
qualities  of  a  good  broken-stone  road  when  subjected  to  heavy 
travel. 

Gravel  roads  may  be  roughly  subdivided  into  two  classes: 

1 .  Those  made  of  gravel  which  has  been  crushed  and  screened 
in   the   same   manner   as   stone.      This  class  of   road   is  con- 
structed  exactly   like   a   stone   road   under  the   same   condi- 
tions, as  described  in  Chapter  VIII. 

2.  Those   made  of  gravel  which  is  used  practically   as  it 
comes  from  the  pit. 

Gravel  roads  can  be  constructed,  as  they  most  often  are, 
by  simply  dumping  the  unscreened  gravel  on  the  road  and 
letting  the  traffic  do  the  rest,  but  this  is  a  poor  and  expensive 
method.  They  can  be  made  by  spreading  the  gravel  in  one 
course  only,  but  so  made  are  not  satisfactory  or  lasting.  To 
make  a  really  satisfactory  and  economic  gravel  road,  the 
gravel  should  be  much  the  same  size  as  is  the  stone  used  for 
stone  roads,  and  should  be  spread  in  two  courses  of  not  over 
6  inches  each,  and  rolled  with  a  7-  or  10-ton  roller. 

Gravel  to  be  used  on  roads  should  be  sharp  and  compara- 
tively clean.     If  it  runs  very  unevenly  in  the  pit  it  should 
be  screened;    the  material  not  going  through  the 
1^-inch  screen  being  used  for  the  first  course  and 
that  going  through  for  the  second.     Even  if  the  gravel  runs 
evenly  there  will  always  be  some  large  stones  and  these  should 
be  thrown  out.     No  stone  larger  than  3  or  4  inches  should  be 
allowed  in  the  road  even  in  the  first  course. 

After  screening,  the  sand  or  clay  left  in  the  gravel  should 
be  no  more  than  just  enough  to  fill  the  voids  in  the  stone, 
and  the  less  it  takes  to  do  this  the  better  the  gravel  is  for 
road  purposes.  After  spreading,  the  gravel  should  be  gone 
over  once  or  twice  with  a  harrow  to  mix  it  thoroughly  and 


124 


THE  ART  OF  ROADMAKING 


to  get  rid  of  small  pockets  of  sand  or  dirt,  which,  however, 
can  often  be  prevented  by  careful  selection  in  the  pit. 


FIG.  84.— Gravel  Road  in  Ohio;  Dries  Quickly  After  a  Rain. 


There  are  a  few  pits  from  which  very  satisfactory  gravel 
roads  can  be  built  by  using  the  gravel  just  as  it  occurs  without 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS 


125 


screening  or  crushing.  A  community  that  has  such  material 
is  blessed  above  all  others.  Even  the  best  of  material,  how- 
ever, must  be  properly  laid  and  rolled  if  permanent  and 
economical  results  are  to  be  secured.  It  does  not  pay  to 
throw  gravel  or  stone  on  the  road  in  the  old  slipshod  way. 
The  subgrade  should  be  prepared  in  the  same  way  as  for 


FIG.  85. — A  Gravel  Road  under  Construction  in  the  Old  Way.  The 
gravel  is  spread  but  no  shoulders  have  been  made  to  hold  it,  and  no 
attempt  is  made  to  get  gravel  of  an  even  quality.  Such  a  road  soon 
wears  into  holes  which  must  be  filled  before  the  road  is  in  good 
condition  for  travel. 


First 
course. 


crushed  stone.     Material  for  the  first   course  should   consist 

of  gravel  of  1^  inch  to  3^  inches  diameter  and  not 

more  than  30  per  cent  of  material  less  than   1^ 

inches  in  size.     This  should  be  spread  evenly  and 

rolled  and  finished  in  the  same  manner  as  the  first  course  of 

stone.     If   it   does   not   consolidate   add   more   clay   and   roll 

again  until  it  is  firm  and  hard  with  an  even  cross  slope. 

The  second  course  of  gravel  should  consist  of  the  gravel 
and  sand  passing  the  1-^-inch  screen,  and  should  contain  not 


126  THE  ART  OF  ROADMAKING 

over   20   per  cent  of  sand   or   clay.     This   should   be   spread 
evenly  to  1 J  times  the  depth  required,  and  harrowed 

Second          an(j  rakec[  until  uniformity  in  the  mixture  is  secured ; 
then  rolled  until  the  whole  is  firm  and  hard,  clay 

being  added  when  necessary  to  make  the  gravel  compact. 
Uncrushed  gravel  needs  no  third  or  binder  course,  and  when 

the  second  course  is  rolled  thoroughly  and  is  smooth  and  hard 

it  is  ready  for  travel. 

SANDY  ROADS 

There  are  many  miles  of  sandy  roads  in  different  parts  of 
the  country,  and  the  remarks  as  to  drainage,  shaping,  etc., 
do  not  apply  to  them  in  their  natural  condition.  The  wetter 
they  are  kept  the  better  they  are.  Sand,  when  confined,  will 
support  almost  any  weight,  the  objection  to  sand  alone  as  a 
road  material  lying  in  the  total  absence  of  any  binding  or 
cementing  qualities.  Sandy  roads  are  good  only  when  damp. 
It  is  useless  to  form  or  crown  sand  roads,  as  they  do  not 
require  drainage.  They  should  be  made  either  flat,  or  lower 
in  the  center  than  at  the  sides,  and  trees  and  undergrowth 
should  be  allowed  to  grow  as  near  the  road  as  possible,  as 
they  help  to  retain  the  moisture.  For  temporary  improve- 
ment of  sandy  roads  a  layer  of  cut  straw,  leaves,  shavings, 
hay,  bark,  sawdust  or  any  material  that  will  accumulate  and 
retain  moisture  and  offer  some  resistance  to  the  wheels,  is  of 
benefit,  but  for  a  semi-permanent  improvement  clay  should 
be  mixed  with  the  sand  in  proper  proportions,  making  a  sand- 
clay  road. 

CLAY  ROADS 

The  clay  road  in  contrast  to  the  sandy  one,  needs  all  the 
drainage  and  crown  possible.  Care  should  be  taken  to  give 
a  clay  road  a  steeper  cross  slope,  to  make  the  ditches  wide, 
to  keep  them  open  and  clean,  and  to  underdrain  spots  where 
the  road  is  especially  bad.  These  are  the  first  essentials,  but 
even  with  these  precautions  a  clay  road  will  never  be  a  good 
road  at  all  times  unless  it  is  treated  with  sand  or  dragged 
with  a  split-log  drag. 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS  127 


SAND-CLAY  ROADS 

In  some  sections  of  the  country  sand  and  clay  are  the  only 
road  materials  available,  and  while  neither  of  these  materials 
alone  makes  satisfactory  roads,  a  proper  combination  of  the 
two,  with  thorough  drainage  and  suitable  crown,  will  produce 
satisfactory  results.  Natural  sand-clay  roads  may  frequently 
be  found  in  localities  where  the  soil  contains  the  right  pro- 
portions of  sand  and  clay.  In  sections  of  the  country  where 
the  prevailing  subsoil  is  composed  entirely  of  clay,  or,  on  the 
other  hand,  is  of  an  extremely  sandy  character,  these  materials 
may  be  mixed  in  such  proportions  so  as  to  overcome  the  most 
objectionable  features  of  each.  The  mixing  of  sand  and  clay 
as  a  form  of  road  construction  has  received  careful  study 
and  is  of  great  importance,  especially  to  the  Atlantic  and 
Gulf  States,  where  throughout  large  areas  sand  and  clay 
arc  practically  the  only  materials  available  for  road  build- 
ing. 

The   essentials   to  success   in  this  form    of   road 
are  puddling  and  saturation.     The  clay   must   be 
rendered   homogeneous   by  adding  water    until  it    is   plastic 
like  dough;  and  to  this  plastic 
clay,  sand  must  be  added  to 
the  point  of    saturation,  but 
not  beyond.     What  is  meant 
by  saturation  may  be  clearly 
understood    by    reference    to 
Fig.  86,  which  shows  a  mag- 
nified   cross-section    of    sand- 
clay    composition     as    found 
in    a     substantial    sand-clay 
road. 

No  sand-clay  road  can  sat- 
isfactorily      withstand        the   FIG.  86.— Clay  Mixed  with  Sand  to 
severity  of  public  travel  with-       the  Point  of  Saturation,  the  angular 
out  having  first  been  reduced      sand  grains  being  in  contacL 
to  a  compact  homogeneous  mass  of  sand  and  clay,  in  which 
each  grain  of  sand  should  be  in  touch  with  other  grains  on 


128 


THE  ART    OF  ROADMAKING 


FIG.  87. — Sand-clay  Mixture  with 
not  enough  Sand,  the  grains  not 
being  in  contact. 


all  sides.     Such   a   condition   is   secured  only  by  a  thorough 

mixing  of  the  wet  clay  and 
sand,  and  rolling  as  the  mix- 
ture dries.  This  forces  the 
particles  of  sand  together,  and 
any  excess  of  clay  tends  to 
rise  to  the  surface,  which  must 
in  turn  be  sanded  and  the 
operations  repeated  until  the 
surface  has  become  hard  and 
compact,  and  free  from  clay- 
stickiness. 

Sand-clay  roads  fail  for 
various  reasons.  Imperfect 
drainage  is  the  first  cause. 
The  imperfections  may  be  in 

the   cross-sectional  drainage,  the  side  ditches,   or  the  drain- 
age of  the    subgrade    or   roadbed.      It    is    cus- 

Causes  of  tomary  to  give  to  a  sand-clay  road  a  little  greater 

crown  than  is  usually  given  to  a  macadam  road, 

especially    where    the    grade    is     above    3    per    cent.     The 

subject  of  side  ditches  should 

have  more  careful  considera- 
tion than  is  usually  given  in 

case  of  macadam  roads. 
If  the   subsoil   is  clay,  the 

bottom   of    the    side    ditches 

should  be  18  inches  or  more 

below  the  crown,  but  if  the 

land  is  rolling  and  the  subsoil 

is  sand  of  considerable  depth, 

there  is  natural  drainage  and 

little  or  no  side  ditch  will  be 

required.     Perhaps  the   most 

common    error    in    drainage 

is      the     failure      to      drain 

properly    and    thoroughly    all   places    where    there    are    wet- 
weather  springs.     If  necessary,  the  roadbed  must  be  changed 


FIG.  88. — Unsatisfactory  Sand-clay 
Mixture,  the  sand  grains  being 
worn  round. 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS  129 

so  as  to  locate  it  upon  dry  gound,  as  even  the  deepest  side 
ditches  practicable  may  fail  to  give  relief  where  such  springs 
exist.  It  is  important  to  avoid  deep  cuts  and  .to  carefully 
consider  all  probable  sources  of  trouble.  Water,  beyond  a 
very  limited  amount,  adds  nothing  of  value  to  the  sand-clay 
road  after  it  is  completed.  If  water  is  always  present,  sand 
should  be  used  without  clay,  as  sand  and  water  make  a  better 
road  than  sand  and  clay  and  water. 


FIG.  89. — Cross-section  of  Road,    showing  lumps  of  clay  placed  on  a  sand 
subsoil  and  covered  with  sand. 

Another  cause  of  failure  is  the  want  of  thorough  mixing 
of  even  the  proper  proportions  of  sand  and  clay.  Clay  in 
lumps  is  useless;  it  should  be  uniformly  saturated  with  sand 
to  a  depth  of  10  inches.  When  ridges  and  holes  appear,  the  high 
places  should  be  leveled  down  and  the  holes  filled  in  with  sand. 

In  northern  sections  frost  is  another  cause  of  failure  and  a 


FIG.  90. — Cross-section  of  Road,  showing  displacement  of  lumps  of  clay 
when  subjected  to  travel. 

difficult  one  to  deal  with.  It  is  temporarily  destructive  and 
for  that  reason  the  mixture  must  extend  below  the  frost-line 
if  the  road  is  built  on  a  clay  foundation.  Freezing  disinte- 
grates the  sand-clay  composition  and  makes  of  it  a  soft,  slushy 
mud,  which,  however,  repacks  again  after  each  heavy  rain, 
although,  as  a  rule,  leaving  the  road  surface  somewhat  rough. 

Failure  is  sometimes  due  to  the  kind  of  sand  selected.  None 
except  sand  made  up  of  angular  grains  is  adapted  to  sand-clay 
road  making.  Sand  with  grains  which  are  worn  off  round, 
or  sand  which  has  been  ground  up  by  the  action  of  wheels 
or  water  until  very  fine,  is  unsatisfactory  and  often  worthless. 
The  use  of  such  material  should  be  avoided,  as  a  perfect  bond 
can  not  be  effected  (Fig.  88),  and  the  road  can  not  resist  the 


a.  Typical  Clay  Road  Before  Improvement. 


6.  Sand-clay  Road  in  Process  of  Construction,  Gainesville,  Fla. 


c.  Finished  Sand-clay  Road,  Columbia,  S.  C. 

FIG.  91.  SAND-CLAY  ROADS.  130 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS  131 

rolling  action  of  wheels,  the  tendency  being  much  the  same  as 
when  pressure  is  applied  to  a  mass  of  marbles. 

Other  causes  of  failure  are  the  improper  selection  of  clay 
and  the  improper  treatment  of  the  clay  used.  Ferruginous 
clays  are  the  best,  and  chalky  clays  are  the  worst  for  road- 
building  purposes.  Some  clays  have  a  large  percentage  of 
sand  to  begin  with  and  require  less  sand,  while  as  a  rule  the 
chalky  (sedimentary)  clays  have  very  little  or  very  fine 
sand,  and  are  more  difficult  to  get  fully  saturated  with 
sharp  sand  so  as  to  become  unyielding  and  homogeneous. 

Another  cause  of  failure  in  the  use  of  this  particular  clay  is 
the  fact  that  it  rarely  has  iron  enough  to  cement  or  bind  the 
material  together;  hence  it  is  easily  broken  up  and  washed 
away  or  blown  away  as  dust.  There  are  many  localities, 
especially  in  the  South,  where  sand  predominates,  and  the 
only  clays  to  be  found  are  sedimentary,  often  carrying  a 
large  percentage  of  very  fine  sand  and  scarcely  any  iron  at 
all.  It  is  difficult  to  build  a  first-class  road  of  this  material; 
but  the  first  step  should  be  to  make  the  roadbed  at  least  20 
inches  above  standing  water  in  the  ditches. 

Lack  of  perseverance  by  the  road  builder  is  another  cause 
of  failure,  and  probably  more  failures  result  from  this  than 
from  any  other  cause.  The  building  of  a  sand-clay  road  is 
a  process,  not  an  instantaneous  operation,  and  the  builder 
may  fail  when  well  within  view  of  success. 

The  building  of  sand-clay  roads  has  passed  the  experimental 
stage,  and  it  is  no  longer  a  question  of  doubtful  procedure. 
The  important  things  to  be  borne  in  mind  are  as  stated,  thorough 
mixing  to  the  saturation  point,  and  then  properly  shaping 
and  rolling  the  road.  This  mixing  might  be  done  by  the  use 
of  plows  and  harrows  when  the  clay  is  wet;  but  it  is  customary 
to  let  the  teams  and  vehicles  of  the  traveling  public  accomplish 
it.  This  is  the  critical  period  in  the  construction  of  a  sand- 
clay  road,  because  care  must  be  taken  to  secure  an  even 
amount  of  puddling,  so  that  all  the  lumps  of  clay  shall  be  broken 
and  saturated  with  sand  to  a  depth  of  8  to  10  inches.  If  this 
can  be  done  and  the  road  is  properly  crowned  as  it  dries,  the 
result  will  be  satisfactory. 


132  THE  ART  OF  ROADMAKING 

It  is,  of  course,  impossible  to  state  definitely  the  cost  of  this 
form  of  construction,   as  it  will  be  found  to  vary  with  the 
price  of  labor,   the  length   of  haul,   the  width   of 
sand-  roadway,    and   depth   and   nature   of   material.     If 

clay  con-  however,  the  clay  can  be  procured  within  a  mile  of 
struction.  ^e  road  which  is  to  be  improved,  and  the  cost  of 
labor  is  about  $1  per  day  and  teams  $3  per  day,  the  cost  of 
constructing  a  12-foot  sand-clay  road  on  a  sand  foundation, 
covered  with  clay  to  an  average  depth  of  6  inches,  would  be 
approximately  as  follows  for  a  distance  of  1  mile:  * 

Crowning  and  shaping  road  with  road  machine,  L.3ing  2  teams  at 

$3  and  1  operator  at  $1.50  per  day  for  1  day $7 . 50 

Loosening,  1173J  cubic  yards  of  clay  with  pick  and  shoveling  into 

wagons,  at  15  cents  per  cubic  yard -. 176 . 00 

Hauling  1173^  cubic  yards  of  clay,  at  23  cents  per  cubic  yard.  .  .  .  269.86 
Spreading  clay  with  road  machine,  using  2  teams  at  $3  and  expert 

operator  at  $1.50  per  day  for  3  days 22 . 50 

Shoveling  sand  on  clay,  estimated  at  ^  cent  per  square  yard 35 . 20 

Plowing,  using  1  team  at  $3  per  day  for  4  days 12 . 00 

Harrowing,  using  1  team  at  $3  per  day  for  2  days 6 . 00 

Shaping  and  dressing  with  road  machine,  using  2  teams  at  $3  and 

expert  operator  at  $1.50  per  day  for  2  days 15.00 

Rolling,  estimated  at  |  cent  per  square  yard 35.20 

Total $579.26 

The  estimated  cost  per  square  yard  of  road  surface,  therefore, 
when  computed  on  the  basis  of  this  table,  would  be  about 
8  cents,  or  at  the  rate  of  $579.26  per  mile. 

The  cost  of  building  a  sand-clay  road  on  a  clay  foundation 
would  not  vary  much  from  the  figures  given.  The  latter  form 
of  construction  would  probably  be  slightly  cheaper,  by  reason 
of  the  fact  that  sand  can  be  handled  more  economically  than 
clay. 

According  to  the  experience  of  the  Office  of  Public  Roads,  the 
cost  of  sand-clay  construction  in  the  South  has  been  found  to 
range  from  $200  to  $1200  per  mile,  in  most  cases  running  from 
$300  to  $800.  In  case  changes  of  grade  have  to  be  made 
with  consequent  cuts  and  fills,  the  cost  would  be  proportionately 
greater  than  the  figures  given  above,  but  there  can  be  no 

*  Office  of  Public  Roads  Bulletin,  No.  27. 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS  133 

question,  that  under  all  circumstances  this  form  of  construction 
is  cheaper  than  macadam. 


BURNT-CLAY  ROADS 

In  some  sections  of  the  country  the  only  material  available 
from  which  roads  can  be  constructed  is  clay.  This  is  especially 
the  case  in  large  areas  in  the  South,  where  there  is  little  or  no 
sand  and  the  clays  are  of  a  particularly  plastic  and  sticky 
variety,  locally  known  as  "gumbo"  and  " buckshot."  In  such 
localities  traffic  is  absolutely  impossible  during  the  wet 
season,  as  the  wheels  of  heavy  vehicles  will  sink  to  the  hub. 
To  meet  this  condition  the  U.  S.  Office  of  Public  Roads  made 
an  experiment  in  the  district  of  the  lower  Mississippi  Valley,  of 
burning  the  clay  along  the  entire  length  of  the  road.  By 
burning  clay,  even  at  a  moderate  heat,  its  sticky  or  plastic 
quality  is  destroyed,  so  that  even  in  the  wettest  weather 
it  will  bear  traffic.  It  was  found  by  laboratory  experiments 
that  the  clinkering  point  of  the  clay  was  sufficiently  low  to 
indicate  that  simple  burning  of  the  lumpy  clays  upon  the 
road  surface  by  means  of  open  wood  fires  would  accomplish  the 
desired  result.  This  permits  the  firing  of  the  clay  along  the 
entire  length  of  the  road,  thus  avoiding  the  cost  of  hauling 
it,  and  at  the  same  time  gaining  the  advantage  of  burning  the 
foundation  of  the  road  as  well  as  the  material  to  be  placed 
upon  it. 

Gumbo  clay  is  black,  owing  to  the  high  percentage  of  organic 
or  vegetable  matter  it  contains.  It  is  particularly  sticky 
in  its  nature,  and  is  almost  wholly  free  from  sand  and  grit. 
After  it  has  been  burned,  however,  the  plasticity  is  entirely 
destroyed,  and  a  light  clinker  is  formed  which,  though  not 
particularly  hard,  when  pulverized  forms  a  smooth  surface 
and  seems  to  wear  well.  It  is  not  necessary  that  all  of  the 
clay  out  of  which  the  road  is  to  be  constructed  should  be 
clinkered,  but  only  a  sufficient  amount  should  be  rendered 
nonplastic  to  neutralize  the  too  sticky  character  of  the  native 
clay. 

Good  sound  wood,  as  dry  and  well  seasoned  as  it  is  possible 


134 


THE  ART  OF  ROADMAKING 


a.  Pile  of  Wood  and  Clay  Completed  and  Firing  Begun. 


Z>.  Section  of  Road  Burned. 
FIG.  92.— BURNT-CLA.Y  ROADS. 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS     135 


c.  Partial  View  of  Finished  Road. 
FIG.  92. — BURNT-CLAY  ROADS. 

to  procure,  is  stacked  at  convenient  intervals  along  the  side  of 
the  road  before  the  work  is  commenced.     About 
one  cord  of  wood  is  necessary  for  8  linear  feet  of 
roadbed  12  feet  wide.     Brushwood,  if  it  is  dry,  as  well  as  chips, 
bark,  old  fence  rails  and  railroad  ties,  coal  slack — in  fact  any 
sort  of  fuel  that   can  be  easily  and  economically  obtained, 
may  be  used  to  advantage  with  the  cord  wood. 

After  grading  the  road  to  an  even  width  between  ditches, 
it  is  plowed  up  as  deeply  as  practicable.     Furrows  are  then 
dug  across  the  road  from  ditch  to  ditch,  extending 
through  and  beyond  the  width  to  be  burned;    if  Preparation 
it  is  intended  to  burn  12  feet  of  roadway,  the  trans-  roadbed 
verse  furrows  should  be  16  feet  long,  so  as  to  extend 
2  feet  on  each  side  beyond  the  width  of  the  final  roadway. 
Across  the  ridges  formed  between  these  furrows,  which  should 
be  about  4  feet  apart,  the   first  course  of   cordwood  is    laid 
longitudinally  so  as  to  form  a  series  of  flues  in  which  the  firing 
is  started — from  15  to  20  of  these  flues  are  fired  at  one  time. 

The  best  and  soundest  cordwood  is  selected  for  this  course 
and  should  be  laid  so  that  the  pieces  will  touch,  thus  forming 


136  THE  :ART  OF  ROADMAKING 

a  floor.  Another  layer  of  wood  is  thrown  irregularly  across 
this  floor,  in  crib  formation,  with  spaces  left  between  in  which 
the  lumps  of  clay  are  piled  in  such  a  way  as  to  allow  a  draft 
for  easy  combustion. 

After  the  lumps  of  clay  have  been  heaped  upon  this  floor, 
another  course  of  wood  is  laid  parallel  to  the  first.  The  third 
layer  is  laid  in  exactly  the  same  manner  as  the  first,  and  each 
opening  and  crack  should  be  filled  with  brush,  chips,  bark, 
small  sticks,  or  any  other  combustible  material.  The  top 
layer  of  clay  is  placed  over  all  and  the  finer  portions  of  the 
material  are  heaped  over  the  whole  structure. 

The  deep  covering  of  clay  which  is  thrown  over  all  should  be 
taken  from  the  side  ditches,  and  may  be  in  lumps  of  all  sizes, 
including  the  very  finest  material.  It  is  spread  as  evenly  as 
possible  over  the  top  in  a  layer  of  not  less  than  6  to  8  inches. 
Finally  the  whole  is  tamped  and  rounded  off  so  that  the  heat 
will  be  held  within  the  flues  as  long  as  possible. 

It  is  necessary  to  get  the  fires  well  under  way  in  the  flues 
before  the  first  layer  of  wood  is  burned  through.  The  first 
action  of  the  fire  is  to  drive  out  the  water  contained  in  the 
clay  before  the  actual  burning  and  clinkering  can  begin.  In 
burning  the  gumbo  clays  a  great  advantage  is  gained  from 
the  organic  and  vegetable  matter  which  is  contained  in  the 
clay,  as  that  in  itself  aids  combustion. 

The  best  results  are  obtained  by  firing  all  the  flues  of  a  section 

simultaneously  and  maintaining  the  combustion  as  evenly  as 

possible.     A  supply  of  light,  dry,  kindling  wood, 

or  any  easily  inflammable  material,  should  be  at 

hand   to    prevent    the   fire    from    dying    down    in    any    one 

place. 

After  the  firing  is  completed  not  only  the  portion  of  clay 
which  forms  the  top  of  the  kiln,  but  the  ridges  between  the 
flues  should  be  burned  thoroughly,  so  as  to  form  a  covering  of 
burnt  clay  10  to  12  inches  in  depth,  which,  when  rolled  down 
and  compacted,  forms  a  road  surface  of  from  6  to  8  inches  in 
thickness.  If  properly  burned,  the  material  should  be  entirely 
changed  in  character,  and  when  it  is  wet  it  will  have  no  tendency 
to  form  mud. 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS     137 

When  the  material  is  sufficiently  cooled  the  roadbed  should 
be  brought  to  a  high  crown  with  a  road  grader  in  order  to 
allow  for  the  compacting  of  the  material.  After  this  the  rolling 
should  be  begun  and  continued  until  the  roadbed  is  smooth 
and  hard.  The  finished  crown  should  have  a  slope  of  at  least 
one-half  inch  to  the  foot. 

The  main  advantages  of  this  method  of  burning  a  road  over 
its  entire  length  are,  first,  that  the  cost  of  transporting  the  clay 
is  avoided;  second,  that  the  subgrade  of  the  road  is  burned  as 
well  as  the  material  above. 

Although  this  form  of  construction  in  the  South  up  to  the 
present  time  has  been  successful,  it  cannot  as  yet  be  said  to 
have  passed  the  experimental  stage,  so  that  the  cost    c        . 
figures  which  will  apply  to  the  same  work  in  all    burnt-clay 
sections    of    the    country    cannot    be    given.     The    construc- 
items  of  cost  of  the  experimental  road  300  feet 
long,  as  constructed  at  Clarksdale,  Miss.,  are  as  follows: 

30£  cords  of  wood  at  $1.30  per  cord $39 .65 

20  loads  of  bark,  chips,  etc 6 . 00 

Labor  at  $1.25  per  day  and  teams  at  $3  per  day 38 . 30 


Total  cost  of  300  feet 83 . 95 

Total  cost  per  mile  at  this  rate 1478 .40 

TOOLS   USED   IN  CONSTRUCTION   OF  COUNTRY  ROADS 

TOOLS  FOR  CLEARING  AND  GRUBBING 
Bush  hooks  (Fig.  93). 
Axes.- 
Grub  hoes. 

Mattocks  (Fig.  94  and  95). 
Stump-pulling  machine. 
Gross-cut  saws. 

TOOLS  FOR  GRADING 
Picks. 

Grading  pick  (Fig.  96) . 
Clay  pick  (Fig.  97). 
Shovels. 
Ploughs  (Fig.  98). 


THE  ART  OF  ROADMAKING 


FIG.  93. — Bush-hooks. 


FIG.  94.— Axe  Mattock.  FIG.  95.— Pick  Mattock. 


FIG.  96. — Grading-pick. 


FIG.  97.— Clay-pick. 


FIG.  98.— Hard-pan  Plough. 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS 


139 


There  are  many  forms  of  ploughs,  known  as  "grading 
ploughs,"  "road  ploughs/'  "breaking  ploughs/'  "hardpan 
ploughs/'  "township  ploughs/'  etc.,  varying  in  construction 


FIG.  99. — Roadscraper. 

according  to  the  kind  of  work  they  are  intended  for,  such  as 
loosening  earth,  gravel,  hardpan,  etc. 

Wheelbarrows  (Fig.  100). 
Scrapers  (Fig.  101-103). 

These  are  made  of  wood  or  pressed  steel  and  are  employed 
in  moving  earth  short  distances,  in  maintenance  and  street- 


FIG.   100. — Dirt  Wheelbarrow. 

cleaning  work.     The  maximum  distance  to  which  earth  can 
be  wheeled  economically  in  barrows  is  about  200  feet. 


140 


THE    ART    OF    ROADMAKING 


SCRAPERS 

Scrapers  are  generally  used  for  moving  material  after  it 
has  been  loosened  by  ploughing.  The  two  principal  varieties 
are  the  drag  and  the  wheel  scraper. 

DRAG  SCRAPER. — The  scoop  (Fig.  101)  is  made  in  three  sizes, 
3  and  7  cubic  feet  capacity.  Some  have  metal  runners  on 


FIG.  101. — Drag-scraper. 

the  bottom,  others  have  a  double  bottom,  which  decreases 
draft  and  increases  durability.  Used  for  moving  earth  short 
distances,  but  unsuitable  for  building  a  bank  of  uniform 


FIG.  102. — Drag-scraper  with  Runners. 

solidity  or  for  finishing  an  embankment,  as  each  scraperful 
is  deposited  in  a  compact  mass  and  the  surface  made  with 
it  is  a  succession  of  lumps  and  hollows.  Sometimes  used  for 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS 


141 


loading  wagons,  by  means  of  an  elevated  platform  and  an 
excavated  runway. 

FLAT-BOTTOMED  POLE  OR  TONGUE  SCRAPER. — Made  in  two 
sizes,  36  and  48  inches  wide.  Used  for  leveling  up  the  road 
surface  in  excavations,  and  in  preparing  the  subgrade  for 
pavements. 

BUCK  SCRAPER. — Made  in  three  sizes,  3£,  4,  and  5  feet 
wide,  with  capacity  of  8,  10,  and  12  cubic  feet,  respect- 
ively. An  improvement  over  the  common  scoop  scraper, 


FIG.  103.— Wheel  Scraper. 

having  the  advantages  of  being  more  readily  loaded  to  its 
full  capacity,  a  better  and  more  uniform  distribution  of  the 
of  the  earth,  more  durable  and  more  easily  loaded. 

WHEEL  SCRAPERS  (Fig.  103)  consist  of  a  steel  box  mounted 
on  wheels  and  furnished  with  levers  for  raising,  lowering,  and 
dumping,  all  movements  being  made  without  stopping  the  team. 
Made  in  three  sizes,  with  capacities  of  9,  12,  and  16  cubic  feet. 

ROAD  GRADERS. — This  is  one  of  the  various  forms  of  road 
machines.  It  is  also  known  as  the  " scraping  grader"  (Fig.  99), 
to  distinguish  it  from  the  "elevating  grader,"  and  is  a  very 
important  factor  in  the  construction  and  maintenance  of  earth 
roads.  It  consists  of  a  frame  carried  on  four  wheels,  support- 


142  THE  ART  OF  ROADMAKING 

ing  an  adjustable  scraper-blade,  the  front  end  of  which  ploughs 
a  furrow  while  the  rear  end  pushes  the  earth  toward  the  center 
of  the  road  or  distributes  it  uniformly  to  form  a  smooth  surface. 
The  blade  is  adjustable  backward  and  forward  and  to  any  angle 
or  height.  It  will  work  in  almost  any  soil.  It  is  hauled  by 
horses  and  makes  successive  rounds  or  cuts  until  the  desired 
depth  of  ditch  and  crown  of  road  is  obtained.  There  are 
several  forms  of  the  machine,  differing  in  minor  details,  but 
all  are  intended  for  practically  the  same  purposes. 

ELEVATING  GRADER,  consists  of  a  frame  carried  on  four 
wheels,  from  which  is  suspended  a  plough  and  a  frame  carry- 
ing a  wide  traveling  inclined  belt.  The  plough  loosens 
the  soil  and  throws  it  upon  the  belt,  which  delivers  it  upon 
the  embankment  or  into  wagons.  The  machine  is  adjustable 
and  is  made  in  two  sizes,  delivering  earth  from  7  to  8  feet  ver- 
tically and  14  to  22  feet  horizontally. 

It  is  a  very  effective  machine  for  building  open  ditches, 
earth  embankments,  filling  of  wagons,  and  for  highway  work. 
By  proper  adjustment  the  machine  will  build  broad  and 
low  or  narrow  and  high  embankments  or  will  excavate  a  deep 
and  narrow  or  a  shallow  ditch. 

The  larger  machine  will  place  1000  cubic  yards  of  earth  in 
an  embankment  in  ten  hours,  or  will  load  600  cubic  yards 
into  wagons  in  the  same  time.  It  is  propelled  by  twelve 
horses,  eight  in  front  and  four  behind,  or  by  a  traction  engine, 
and  is  operated  usually  by  three  men. 

The  smaller  machine  will  grade  a  quarter  of  a  mile  of 
ordinary  unbroken  road  per  day,  with  a  width  of  25  to  30 
feet  and  a  crown- of  12  inches  at  the  center.  It  is  drawn  by 
eight  horses  and  operated  by  two  men. 

These  machines  are  specially  adapted  to  building  earth  roads 
in  a  prairie  country,  for  which  purpose  they  are  very  largely  used. 

CARTS.  —These  carts  are  furnished  with  wide  tires  and  the 
body  is  so  balanced  that  the  load  is  evenly  divided  above  the 
axle.  The  average  capacity  is  22  cubic  feet  and  the  average 
weight,  about  800  pounds. 

DUMP  CARS. — Made  to  dump  on  one  or  both  sides  or  ends, 
and  at  the  bottom.  They  are  used  singly  or  in  trains,  according 


EARTH,   GRAVEL,  SAND  AND  CLAY  ROADS 


143 


144 


THE  ART  OF  ROADMAKING 


to  the  magnitude  of  the  work,  and  are  drawn  by  horses  or 
tractors. 

DUMP  WAGONS. — The  use  of  these  wagons  for  moving 
excavated  earth,  etc.,  and  for  transporting  sand,  gravel,  and 
other  materials,  materially  shortens  the  time  required  for 


No.  I. 


No.  7. 


FIG.  105. — Draining-tools. 


Nos.  3,  4,  and  5,  used  for  digging  the  ditch;  Nos.  6  and  7  for  cleaning  and  rounding 
the  bottom  of  the  ditch  for  round  tile.  No.  2  for  shoveling  out  loose  earth  and  leveling 
the  bottom  of  the  ditch;  No.  1  for  the  same  purpose  when  the  ditch  is  intended  for 
"sole"  tile. 

unloading  over  that  required  by  the  ordinary  form  of  con- 
tractor's wagon.  They  are  operated  by  the  driver  and  have 
a  capacity  of  from  35  to  45  cubic  feet. 

SURFACE  GRADER. — Is  operated  by  one  horse  and  is  used  for 
removing  earth  previously  loosened  by  the  plough.  It  is  also 
used  to  level  off  and  trim  the  surface  after  scrapers. 

ROAD    LEVELER. — Is     used    for   trimming    and    smoothing 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS     145 

the  surface   of    earth   roads   and    is   largely  employed  in  the 
spring  when  the  frost  leaves  the  ground. 

DRAINING  TOOLS. — These  are  used  for  digging  the  ditches 
and  sloping  the  bottom  to  fit  the  drain-tiles. 

THE  EARTH-ROAD  DRAG  * 

During  the  last  few  years  a  great  deal  has  been  written  on  the 
subject  of  the  earth-road  drag  and  its  uses.  Great  changes 
in  the  general  condition  of  many  roads  have  been  produced 
by  the  use  of  this  simple  tool,  and  several  states  have  passed 
special  laws  allowing  towns  to  make  provisions  for  dragging 
all  their  clay  roads  after  each  rain. 

The  drag  is  not  a  cure  for  all  evil  roads,  but  if  it  is  used  at 
the  proper  time  and  on  proper  soils  it  will  produce  a  road  good 
for  travel  at  times  when  the  road,  if  undragged,  would  be  an 
impassable  mud  hole. 

The  question  as  to  whether  to  shape  up  a  road  before  drag- 
ging is  one  that  can  only  be  decided  by  the  character  of  the 
present  road  surface.  If  this  is  badly  out  of  shape,  narrow, 
with  no  ditches,  or  much  higher  on  one  side  than  Requisites 
on  the  other,  it  is  best  to  plough  it  a  furrow  at  a  time  for  success, 
and  form  it  up  with  the  road  machine  to  shape  approximately 
as  shown  in  Fig.  80,  which  is  the  proper  shape  for  a  dragged 
road.  Not  quite  as  great  a  cross  slope  should  be  given  in 
order  to  allow  for  material  being  pulled  to  the  center  by 
the  drag.  If  the  road  is  fairly  well  shaped  and  of  the  proper 
width  it  is  ready  for  dragging  at  any  time  after  the  drainage 
has  been  attended  to. 

The  road  must  have  proper  surface  drainage  or  it  is  use- 
less to  drag  it.  Wherever  the  road  is  continually  soft  and 
spongy  from  underground  water  tile  under-drain  should  be 
put  in.  Ditches  should  be  kept  clean  and  open  at  all  times 
and  proper  culverts  and  bridges  provided  where  necessary.* 
The  drag  will  smooth  the  surface  so  that  water  is  quickly 

*  Condensed  from  Road  Pamphlet,  No.  2,  "The  Earth  Road  Drag," 
by  Arthur  R.  Hirst,  Highway  Engineer,  issued  by  the  Wisconsin  Geo- 
logical and  Natural  History  Survey. 


146  THE  ART  OF  ROADMAKING 

carried  to  the  ditches,  but  in  order  that  dragging  may  be 
fully  effective  it  is  necessary  that  the  water  should  be  quickly 
carried  away  by  the  ditches  and  culverts. 


(From  Technical  World  Magazine) 
FIG.  106.— A  Country  Road  Dragged  with  the  King  Split-log  Drag. 

The  exact  form  or  style  of  drag  to  be  used  is  not  the  most 

essential  part  or  road  dragging.     Almost  any  device  will  prove 

effective  which  will  move  a  small  amount  of  earth 

towards  the  middle  of  tne  road  and  at  the  same 
time  smooth  the  surface.  As  the  whole  theory 
and  effectiveness  of  road  dragging  depends  on  the  moving 
of  but  a  small  amount  of  earth  at  a  time,  it  is  important  that 
no  road  drag  be  used  which  is  heavy.  In  fact,  the  lighter  and 
more  simple  the  drag  the  more  effective  it  usually  is. 

A  simple  stick  of  timber  or  piece  or  railroad  iron  has  proved 
useful  for  this  work.  V-shaped  drags  have  also  been  used, 
but  seem  to  be  objectionable,  on  account  of  their  heavy 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS  147 

draft.  Perhaps  the  most  effective  form  of  drag  is  that 
known  as  the  "split-log  drag/'  which  may  also  be  made  of 
two  stout  planks  in  place  of  the  split  log.  Oak  or  other  heavy 
wood  should  not  be  used  where  it  is  possible  to  get  a  log  of 
lighter  wood. 

Figures  107  and  108  show  two  varieties  of  split-log  drags 
which  are  so  simple  in  construction  that  they  can  be  made  on 
every  farm.  The  log  should  be  from  8  to  12  inches  in  diameter 
and  from  7  to  9  feet  long.  The  holes  in  the  front  half  of  the 
log  should  be  bored  so  that  a  slight  slant  forward  is  given  to 
the  lower  part  of  the  front  face  of  the  split  log.  The  holes 
in  the  rear  log  are  bored  so  that  its  flat  face  will  be  perpendicular 
to  the  sticks  forming  the  connecting  braces,  which  should  be 
tapered  at  the  ends  so  that  they  will  fit  snugly  into  the  holes 
bored  into  the  logs.  The  holes  should  not  be  less  than  2  inches 
in  diameter.  The  ends  of  the  cross  sticks  should  be  split 
and  wedges  driven  so  as  to  secure  the  cross-braces  in  place. 
The  wedges  should  be  driven  crosswise  of  the  grain  of  the  log 
or  plank  so  as  not  to  split  it.  A  diagonal  cross-brace  is  placed 
between  the  logs  at  the  leading  end  to  stiffen  the  frame  of  the 
drag.  The  distance  from  the  face  of  the  back  log  to  the  face 
of  the  front  log  should  be  about  2^  or  3  feet.  The  lower  front 
edge  or  toe  of  the  drag  should  be  protected  by  a  strip  of  old 
wagon  tire,  or  other  piece  of  iron  about  a  quarter  of  an  inch 
thick,  3  or  4  inches  wide  and  about  4  feet  long.  This  strip 
of  iron  should  be  bolted  to  the  front  log  and  the  heads  of  the 
bolts  countersunk.  The  strip  of  iron  should  not  be  carried 
the  entire  length  of  the  front  log. 

Chains  should  be  provided  with  which  to  haul  the  drag, 
arranged  with  a  short  and  long  hitch  as  shown  in  the  sketch, 
so  that  the  drag  will  travel  at  an  angle  of  about  forty-five 
degrees  with  the  direction  of  the  road. 

Before  giving  instructions  for  operating  a  drag,  it  is  well 
to  keep  in  mind  the  objects  to  be  attained  by  this  method 
of   road    maintenance,    which   are   to    smooth   the    object  of 
surface  of  the  road  when  it  is  soft  and  muddy,  to    r°ad  drag- 
move  a  small  amount  of  moist  earth  to  the  center,    gmg* 
and  to  maintain  the  crown  or  oval  shape  of  the  road. 


148 


THE  ART  OF  ROADMAKING 


FIG.  107. — Split-log  Drag  Recommended  by  the  Wisconsin  Geological 
and  Natural  History  Survey. 


(From  Technical  World  Magazine) 
FIG.  108. — The  D.  W.  King  Split-log  Drag  used  extensively  in  Missouri. 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS  149 

The  drag  is  not  an  implement  to  use  to  move  large  quan- 
tities or  earth,  nor  does  the  maintenance  of  an  earth  road  re- 
quire the  use  of  such  an  implement.  A  consideration  of  the 
theory  of  road  dragging  will  help  to  make  the  use  of  the  drag 
more  fully  understood. 

If  a  sample  of  moist  earth  is  taken  from  the  traveled  por- 
tion of  a  road  over  a  clay  soil,  it  will  be  found 
practically  impervious  to  water.  Theory  of 


Earth  in  this  condition  is  what  the  clay  workers      j£*    in 
call  "  puddled.''    It  has  been  worked  and  reworked 
by  the  carriage  wheels  and  animals'  hoofs  until  nearly  all  the 
traveled  portion  of  a  sticky,  muddy  road  is  covered  with  a 
layer  of  this  impervious,  puddled  earth. 

As  usually  found  on  most  of  the  roads,  this  puddled  earth 
is  full  of  holes  and  ruts,  which  are  filled  with  water  that  can- 
not escape  through  the  impervious  soil.  As  long  as  the  water 
remains  the  soil  cannot  dry  out  and  the  road  is  kept  in  a  most 
uncomfortable  if  not  impassable  condition. 

It  is  also  a  matter  of  observation  that  this  puddled  earth 
when  compressed  and  dried  becomes  extremely  hard.  On 
these  two  facts,  the  imperviousness  of  puddled  earth  and  its 
hardness  when  dried,  rests  the  theory  of  road  dragging. 

When  the  road  drag  is  properly  used  it  spreads  out  the 
layer  of  impervious  soil  over  the  surface  of  the  road,  filling 
up  the  ruts  and  hollows  until  a  smooth  surface  is 
secured.     As  a  small  amount  of  material  is  always  The  effect 
to   be   pushed   to   the   center,    a   slightly   rounded 
effect   will  be  given  to  the  road,   which  may  be 
increased   or   decreased   as   desired   by   subsequent   dragging. 
By  forcing  the  mud  into  the  hollows  and  ruts  it  is  evident 
that  the  water  must  go  out,  which  it  does  by  running  off  to  the 
side  of  the  road.     The  drying  out  of  the  road  is  thus  much 
facilitated  and  the  road  is  made  immediately  firmer. 

The  effect  of  traffic  over  the  road  tends  to  press  down  and 
thoroughly  compact  each  thin  layer  of  puddled  earth  which 
the  drag  spreads  over  the  surface  every  time  it  is  used.  After 
the  first  few  draggings  the  road  becomes  constantly  smoother 
and  harder  so  that  the  effect  of  a  rain  is  scarcely  noticeable, 


150 


THE  ART  OF  ROADMAKING 


> 


FIG.  109. — Where  Brooks  flow  in  the  Wagon  Ruts,  showing  how  a  danger- 
ous quagmire  gets  its  start. 


FIG.  110. — Part  of  same  stretch  of  Road  after  Dragging. 

(From  Technical  World  Magazine) 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS  151 

the  water  running  off  the  surface,  which  is  so  smooth  and  hard 
as  to  absorb  but  little  of  it. 

The  following  points  are  to  be  borne  in  mind  in  dragging 
a  road. 

Make  a  light  drag,  which  is  hauled  over  the 

road    at    an    angle    so   that  a  small  amount  of     Jnst™ctions 

for  dragging, 
earth  is  pushed  to  the  center  of  the  road. 

Drive  the  team  at  a  wralk. 

Ride  on  the  drag;    do  not  walk. 

Begin  at  one  side  of  the  road,  returning  on  the  opposite 
side. 

Drag  the  road  as  soon  after  every  rain  as  possible,  but  not 
when  the  mud  is  in  such  a  condition  as  to  stick  to  the  drag. 

Do  not  drag  a  dry  road. 

Drag  whenever  possible  at  all  seasons  of  the  year.  If  a 
road  is  dragged  immediately  before  a  cold  spell  it  will  freeze 
in  a  smooth  condition. 

The  width  of  traveled  way  to  be  maintained  by  the  drag 
should  be  from  18  to  20  feet;  first  drag  a  little  more  than  the 
width  of  a  single  wheel  track,  then  gradually  increase  until 
the  desired  width  is  obtained. 

Always  drag  a  little  earth  towards  the  center  of  the  road 
until  it  is  raised  from  10  to  12  inches  above  the  edge  of  the 
traveled  way. 

If  the  drag  cuts  in  too  much,  shorten  the  hitch. 

The  amount  of  earth  that  the  drag  will  carry  along  can 
be  very  considerably  controlled  by  the  driver,  according  as 
he  stands  near  the  cutting  end  or  away  from  it. 

When  the  roads  are  first  dragged  after  a  very  muddy  spell 
the  wagons  should  drive  if  possible  to  one  side  until  the  road- 
way has  a  chance  to  freeze  or  partially  dry  out. 

The  best  results  from  dragging  are  obtained  only  by  re- 
peated applications. 

The  following  suggestions  for  using  the  drag  are  taken  from 
the  monthly  bulletin  of  the  Missouri  Board  of  Agriculture 
for  April,  1906. 

1.  "The  length  of  the  chain,  which  is  regulated  by  slipping 
it  backward  or  forward  through  the  hole  in  ditch  end  of  drag, 


152  THE  ART  OF  ROADMAKING 

regulates  the  hold  taken  on  the  earth.  To  make  the  chain 
longer  is  equivalent  to  putting  weight  on  the  drag.  If  the 
drag  is  too  heavy  shorten  the  chain." 

2.  "The  position  of  the  snatch  hook,  which  attaches  the 
double-trees.     To  move  much  dirt  or  cut  small  weeds  hitch 
the  hook  ftlose  to  the  ditch  end  of  the  drag  and  stand  as  nearly 
on  the  end  of  the  front  slab  as  is  safe.     Drive  very  slowly 
when  thus  hitched.     This  one  hitch  seems  to  be  the  hardest 
to  learn.     The  others  suggest  themselves." 

3.  "  Position  of  the  driver  on  the  drag.     To  move  dirt  see 
above.     In  a  soft  spot  stand  on  rear  slab.     On  a  hard  spot 
stand  on  front  slab  and  drive  slowly.     If  the  drag  clogs  with 
straw,  weeds,  sod  or  mud,  step  to  a  point  as  far  as  possible 
from  ditch  end  of  the  drag.     To  drop  dirt  in  a  low  place  step 
quickly  from  ditch  end  to  other  extreme.     To  fill  a  low  place 
or  mud  hole  nicely  is  the  severest  test  of  skill  with  a  drag." 

4.  "  Presence  or  absence  and  sharpness  or  dullness  of  the 
steel.     The  steel  may  project  half  an  inch  below  the  wood 
at  the  ditch  end  of  the  steel,  but  should  come  up  flush  with 
the  wood  at  other  end  of  the  steel.     After  a  clay  or  gumbo 
road  has  been  dragged  four  or  five  years  the  soil  becomes  so 
tough  and  putty-like  that  one  must  study  it  closely  to  know 
what  to  do.     Sometimes  the  sharp  edge  of  steel  is  used ;   some- 
times the  dull  edge  (holes  are  bored  in  both  edges  of  steel  so 
that  it  can  be  turned  upside  down  and  same  bolt  holes  used) , 
and  sometimes  the  plain  wood.     This   can  be  learned  only 
by  experience." 

To  one  unacquainted  with  the  results  obtained  by  the  use 
of  the  drag  it  seems  unbelievable  that  so  much 
good  can  be  done  with  so  simple  an  instrument. 

No  definite  rule  can  be  laid  down  as  to  the  best  time  to 
drag.  If  traffic  amounts  to  practically  nothing  the  wetter 
the  road  is  the  better.  Ordinarily  however,  it  is  useless  to 
drag  a  road  when  it  is  so  wet  the  mud  flows  or  so  dry  that  it 
pulverizes.  The  best  time  is  when  the  mud  passes  along 
the  front  edge  of  the  drag  without  balling  or  sticking  and 
packs  easily  into  ruts  and  holes  under  pressure  from  the  rear 
log  and  subsequent  travel.  The  best  time  may  be  as  soon 


EARTH,  GRAVEL,  SAND  AND  CLAY  ROADS  153 

as  the  rain  stops  on  some  roads  and  hours  afterward  on  others. 
Each  man  must  find  out  for  himself,  by  experience  on  his 
own  piece  of  road,  the  proper  time  to  drag  it.  In  general, 
it  will  be  found  best  to  start  right  after  the  rain,  especially 
when  first  starting  to  drag  a  road  into  shape,  as  throwing  clay 
into  the  ruts  drives  the  water  out  and  the  road  dries  much 
quicker.  It  is  a  good  thing,  however,  to  drag  a  road  at  almost 
any  time  with  almost  any  kind  of  drag. 


CHAPTER  VIII 
BROKEN-STONE   ROADS 

A  BROKEN-STONE  road  is  one  built  of  small  fragments  of 
stone  laid  on  a  suitable  earth  foundation  and  compacted 
together  into  a  solid  mass.  It  is  uncertain  just  when  this 
system  of  road  construction  was  invented,  but  as  near  as  can 
be  ascertained,  the  first  systematic  construction  of  broken- 
stone  pavements  was  carried  on  in  France  in  1764  by  M. 
Tresaguet,  who  built  many  miles  of  such  pavements  in  the 
latter  part  of  the  eighteenth  century.  In  the  early  part  of  the 
nineteenth  century  two  systems  were  introduced  into  England  f 
the  first  by  Telford,  the  second  by  Macadam.  From  these  two 
pioneers  of  good  roads,  modern  engineers  have  drawn  the 
principles  upon  which  all  present-day  broken-stone  roads  are 
built.  Such  roads  are  generally  known  as  "macadam"  roads; 
the  material  itself  is  often  called  " macadam,"  and  the  work 
of  construction,  "macadamizing."  These  roads  are  also 
sometimes  called  "telford"  roads,  but  this  term  is  more 
appropriately  restricted  to  a  particular  form  of  rough  stone 
foundation  for  a  broken-stone  road.  Neither  is  the  term 
"macadam"  altogether  appropriate  as  a  synonym  for  a  broken- 
stone  road,  but  should  strictly  be  used  only  to  designate  the 
foundation  or  lower  course  of  a  stone  road  composed  entirely 
of  small  fragments. 

The  difference  between  the  methods  of  Telford  and  Macadam 
is  mainly  on  one  point  and  has  been  more  dwelt  upon  than  the 
similarity  of  their  systems  on  many  other  points 
between  on  which  they  both  differed  so  widely  from  the 
methods  of  practice  of  their  predecessors.  Both  insisted  on 
Telford  and  ^  necessity  fOr  the  thorough  drainage  of  the  road- 
bed, a  thing  then  utterly  neglected;  both  made  use 
of  materials  broken  to  gauge  to  form  a  solid  hard  surface  of 

154 


BROKEN-STONE  ROADS 


155 


uniform  cross-section,  and  of  a  surf  ace  curvature  just  sufficient 
to  throw  the  rain  water  off  freely  to  the  sides.  The  distinc- 
tion usually  drawn  between  the  Telford  system  and  that  of 
Macadam  is  in  the  foundation  of  large  stones  upon  which 
Telford  generally  laid  the  broken  ^tone  or  gravel. 

To  Macadam  is  due  the  credit  of  having  been  the  first  to 
direct  public  attention  to  the  necessity  of  the  proper  breaking 
and  preparation  of  road  materials,  and  to  the  possibility  of 
forming  with  them  a  compact  road  surface  nearly  impenetrable 
to  water,  which  can  be  laid  so  flat  as  to  allow  vehicles  to  pass 
freely  over  all  parts  of  the  road,  and  at  the  same  time  throw 
off  the  water. 


FIG.  111. — Cross-section  of  Typical  European  Roads  before  the  time  of 

Macadam. 

What  the  process  of  roadmaking  and  road-mending  was  in 
the  early  part  of  the  nineteenth  century  is  thus  described  by 
Macadam: 

"The  practice  common  in  England,  and  universal  in  Scotland, 
on  the  formation  of  a  new  road,  is  to  dig  a  trench  below  the 
surface  of  the  ground  adjoining,  and  in  this  trench  to  deposit 
a  quantity  of  large  stones ;  after  this  a  second  quantity  of  stone, 
broken  smaller,  generally  to  about  seven  or  eight  pounds  weight; 


FIG.  112. — Cross-section  of  a  Typical  English  Road  a  Hundred  Years  Ago, 
showing  method  of  making  repairs. 

these  previgus  beds  of  stone  are  called  the  bottoming  of  the 
road,  and  are  of  various  thicknesses,  according  to  the  caprice 
of  the  maker  and  generally  in  proportion  to  the  sum  of  money 
placed  at  his  disposal.  On  some  new  roads  made  in  Scotland 
in  the  summer  of  1819,  the  thickness  exceeded  three  feet. 


156  THE  ART  OF  ROADMAKING 

"That  which  is  properly  called  the  road  is  then  placed  on 
the  bottoming,  by  putting  a  large  quantity  of  broken  stone  or 
gravel,  generally  a  foot  or  eighteen  inches  thick,  at  once  upon 
it,  and  from  the  careless  way  in  which  it  is  done  the  road  is  as 
open  as  a  sieve  to  receive  the  water,  which  is  retained  in  the 
trench/7  * 

With  respect  to  repairs,  he  says  that  there  seemed  to  be 
"no  other  idea  of  mending  a  road  than  bringing  a  great  quan- 
tity of  material  and  shooting  it  on  the  ground." 


John  Loudon  Macadam  was  born  on  September  21,  1756, 
in  Ayr,  Scotland,  where  his  father  was  a  landed  proprietor 
and  founder  of  the  first  bank  in  the  town.  He  was 
John  educated  in  the  parish  school,  and  is  said  to  have 

Macadam  shown  an  early  inclination  towards  road  construction 
by  making  a  model  of  a  road  in  the  district.  On  the 
death  of  his  father  in  1770,  he  was  sent  to  his  uncle,  William 
Macadam,  a  merchant  in  the  city  of  New  York,  from  whom  he 
received  his  business  training.  During  the  American  Revolu- 
tionary War  he  acted  as  an  agent  for  the  sale  of  prizes  taken  in 
battle,  and  on  the  declaration  of  peace,  in  1783,  he  returned  to 
Scotland,  having  remained  loyal  to  the  King  of  England. 

After  his  return  to  Scotland  he  was  for  thirteen  years  a 
member  of  the  Commission  of  Peace,  and  Deputy  Lieutenant  of 
the  County.  During  the  Napoleonic  wars  he  raised  a  volunteer 
corps  of  artillery  for  the  defense  of  the  coast  and  was  com- 
missioned as  a  major. 

During  this  period,  as  trustee  on  certain  highways,  he  carried 
on  experiments  at  his  own  expense,  arid  in  the  face  of  great 
opposition  he  succeeded  in  improving  the  roads  under  his 
jurisdiction.  The  Highland  Rebellion  of  1745  had  given  an 
impetus  to  road  building  in  Scotland,  though  these  roads  were 
chiefly  for  military  purposes.  Between  1760  and  1780  more 
than  600  Turnpike  Acts  were  passed,  but  the  roads  actually 
built  under  this  authority  were  constructed,  as  a  rule,  with- 
out system  or  technical  knowledge. 

*  <;  Remarks  on  the  Present  System  of  Road  Making,"  etc.,  by  John 
Loudon  Macadam,  1820. 


BROKEN-STONE  ROADS  157 

In  1798,  Macadam  moved  to  Bristol,  England,  and  engaged 
in  business  connected  with  the  victualing  of  the  navy,  but  he 
spent  much  time  in  private  travel  about  the  kingdom  in  the 
investigation  of  roads  and  the  various  methods  of  construction 
and  repair  then  in  operation.  By  August,  1814,  he  had 
traveled  30,000  miles  and  had  expended  from  his  private  purse 
over  $25,000,  but  had  gained  experience  that  made  him  a 
recognized  authority  on  road  building  and  made  his  advice 
eagerly  sought  for  by  those  having  charge  of  roads,  while  his 
views  were  boldly  expressed  in  print  and  before  several  parlia- 
mentary committees.  The  first  recorded  practical  application 
of  his  knowledge,  on  a  large  scale,  followed  his  election  as  a 
trustee  of  the  Bristol  Turnpike  Trust.  He  found  the  roa<^  of 
that  district  in  a  very  bad  condition,  and  on  Jan.  16,  1816, 
he  was  appointed  surveyor  for  the  trust,  in  direct  charge  of 
construction  and  repairs.  His  salary  was  at  first  $2000  per 
year,  and  later  $2500,  and  out  of  this  sum  he  had  to  pay  his 
traveling  and  other  expenses,  amounting  to  about  $1000  per 
annum.  The  roads  under  his  management  aggregated  149 
miles  in  length,  but  this  was  later  increased  to  178  miles. 
In  June,  1817,  he  was  enabled  to  report  that  none  of  the  roads 
in  the  Bristol  District  wTere  in  bad  condition;  the  cost  of 
maintenance  had  largely  decreased;  the  income  had  .increased 
in  proportion;  a  floating  debt  of  $7000  had  been  paid  off,  and 
the  principal  debt  had  been  reduced  by  $3650. 

His  work  as  surveyor  to  the  Bristol  Trust  did  not  engage 
his  whole  time,  and  by  1819  he  had  been  consulted  by  thirty-four 
different  bodies  of  road  commissioners,  representing  thirteen 
counties.  In  1823  he  had  reported  to  seventy  sets  of  com- 
missioners in  twenty-eight  counties;  and  of  these  the  roads  in 
thirty-two  trusts  were  being  managed  by  Mr.  Macadam  and 
his  sons  according  to  the  system  devised  by  him,  and  the  work 
done  by  men  trained  under  him.  Macadam  received  no 
compensation  for  this  extra  work  other  than  his  traveling 
expenses,  and  in  the  cases  where  the  road  trusts  were  very  poor 
he  did  not  receive  his  expenses. 

The  opposition  to  the  Macadam  system  of  road  building  was 
formidable  at  first,  the  chief  objection  being  that  the  ramming 


158  THE  ART  OF  ROADMAKING 

of  the  bed  was  unnatural  and  ineffective,  and  was  damaging 
to  the  wheels  of  vehicles  and  to  the  feet  of  the  horses,  but  the 
critics  failed  to  remember  that  previous  to  the  improve- 
ment of  roads  on  the  Macadam  system  the  average  life  of  a 
coach-horse  was  only  three  years. 

In  1817  Macadam  put  clown  the  first  piece  of  macadamized 
road  in  London,  by  improving  the  approaches  to  Blackfriars 
and  Westminster  bridges.  George  IV.  took  a  strong  personal 
interest  in  the  improvement  of  London  streets,  which  fact 
induced  Macadam  to  leave  Bristol  in  1823  and  take  up  his 
residence  within  a  few  miles  of  London.  In  this  same  year  he 
succeeded  in  getting  an  inquiry  before  a  committee  of  the  House 
of  Commons  as  to  his  system,  and  he  had  constructed  a  full 
set  of  road-making  implements,  so  that  he  could  better  explain 
the  principles  of  his  method.  As  a  result,  the  merits  of 
macadamized  roads  were  publicly  admitted  and  acknowledged, 
and  Parliament  voted,  first,  $10,000,  and  later  raised  this  to 
$40,000,  to  compensate  him  for  the  money  he  had  personally 
expended  in  bringing  his  system  into  practical  and  general 
use.  He  declined  a  baronetcy,  but  in  1827  he  was  appointed 
Surveyor-General  to  the  Commissioners  of  Metropolitan 
Turnpike  Roads,  and  his  system  was  adopted  throughout  the 
kingdom.  He  died  Nov.  26,  1836. 

Thomas  Telford  was   born  in  the   district   of  Eskdale,   in 
Scotland,  on  August  9,  1757,  and  obtained  the  rudiments  of 
his  education  in   the  parish  school  at  Westerkirk. 
^e  ^earnec^  ^ne  trade  of  a  mason,  then  took  up 
architecture  in  Edinburgh  and  later  in  London,  and 
being  a  man  of  exceptional  ability,  he  soon  established  himself 
as  a  leading  engineer. 

He  became  a  bridge  builder  of  note,  making  this  his  special 
study,  but  he  also  carried  out  many  other  engineering  works, 
particularly  that  of  locating  and  constructing  new  roads  in 
all  parts  of  Great  Britain.  His  first  undertaking  as  a  road- 
maker  on  an  extensive  scale  was  in  the  Highlands  of  Scotland, 
where  he  was  sent  by  the  government  in  1802  to  report  as  to 
the  best  means  of  developing  the  resources  of  the  country. 
He  advised  the  opening  out  of  the  country  by  a  complete 


BROKEN-STONE  ROADS  159 

system  of  roads,  so  as  to  bring  the  interior  parts  into  communica- 
tion with  the  towns  and  the  coast. 

Under  his  direction,  and  by  the  aid  of  parliamentary  grants 
amounting  to  nearly  one  million  dollars,  about  920  miles  of 
road  were  scientifically  laid  out  and  constructed,  and  owing  to 
the  hilly  and  rugged  nature  of  the  country,  works  of  considerable 
magnitude  had  to  be  undertaken,  including  1117  bridges. 
This  work  was  carried  out  in  the  course  of  eighteen  years, 
under  120  contracts,  and  without  recourse  to  a  court  of  law 
in  any  one  instance. 

No  work  on  roads  is  written  to-day  without  an  explanation 
of  Macadam's  and  Telford's  principles,  so  it  will  not  be  out  of 
place  to  mention  them  and  to  discuss  them  in  connection  with 
the  more  extended  knowledge  and  better  appliances  of  the 
present  day. 

The  following  specifications  show  the  difference  in  the  methods 
of  the  inventors. 

TRESAGUET'S  METHOD,  1764  (Fig.  113).—  "The  bottom  of 
the  foundation  is  to  be  parallel  to  the  surface  of  the  road. 
The  first  bed  or  foundation  is  to  be  placed  on  edge 
and  not  on  the  flat,  in  the  form  of  a  rough  pave- 
ment,  and  consolidated  by  beating  with  a  large 
hammer;  but  is  unnecessary  that  the  stones  should  be  even 
one  with  the  other.  The  second  bed  is  to  be  equally  placed 


i  i 

FIG.  113.  —  Cross-section  of  French  Road  Built  by  Tresaguet. 

by  hand,  layer  by  layer,  and  beaten  and  broken  coarsely  with 
a  large  hammer,  so  that  the  stones  may  wedge  together  and 
no  empty  spaces  remain.  The  last  bed,  three  inches  in  thick- 
ness, is  to  be  broken  to  about  the  size  of  a  nut  with  a  small 
hammer,  or  a  sort  of  anvil,  and  thrown  upon  the  road  without 
a  shovel  to  form  the  curved  surface.  Great  attention  must 
be  given  to  choose  the  hardest  stone  for  the  last  bed  even  if 
one  is  obliged  to  go  to  more  distant  quarries  than  which  furnish 
the  stone  for  the  body  of  the  road.  The  solidity  of  the  road 


160  THE  ART  OF  ROADMAKING 

depending  on  this  latter  bed,  one  cannot  be  too  scrupulous  as 

to  the  quality  of  the  materials  which  are  to  be  used  for  it." 

TELFORD'S  METHOD,  1824  (Fig.   114). — "  Upon  the  level  bed 

prepared  for  the  road  materials  a  bottom  course  or  layer  of 

stones  is  to  be  set  by  hand  in  the  form  of  a  close, 
method  ^rm  Pavement-  The  stones  set  in  the  middle  of  the 

road  are  to  be  seven  inches  in  depth;  at  nine  feet 
from  the  center,  five  inches;  at  twelve  feet  from  the  center, 
four  inches;  and  at  fifteen  feet  from  the  center,  three  inches. 
They  are  to  be  set  on  their  broadest  edges  lengthwise  across 
the  road,  and  the  breadth  of  the  upper  edge  is  not  to  exceed 
four  inches  in  any  case.  All  the  irregularities  of  the  upper 
part  of  the  said  pavement  are  to  be  broken  off  by  the  hammer, 
and  all  the  interstices  to  be  filled  with  stone  chips  firmly  wedged 
or  packed  by  hand  with  a  light  hammer,  so  that  when  the  whole 
pavement  is  finished  there  shall  be  a  convexity  of  four  inches 
in  the  breadth  of  fifteen  feet  from  the  center. 


FIG.  114. — Telford's  Shrewsbury  and  Holyhead  Road. 

"The  middle  eighteen  feet  of  pavement  is  to  be  coated  with 
hard  stones  to  the  depth  of  six  inches.  Four  of  these  six 
inches  to  be  first  put  on  and  worked  in  by  carriages  and  horses; 
care  being  taken  to  rake  in  the  ruts  until  the  surface  becomes 
firm  and  consolidated,  after  the  remaining  two  inches  are  to 
be  put  on. 

"The  paved  spaces  on  each  side  of  the  middle  eighteen  feet 
are  to  be  coated  with  broken  stones  or  well-cleaned  gravel 
up  to  the  footpath  or  other  boundary  of  the  road,  so  as  to 
make  the  whole  convexity  of  the  road  six  inches  from  the  center 
to  the  sides  of  it,  and  the  whole  of  the  materials  are  to  be 
covered  with  a  binding  of  an  inch  and  a  half  of  good  gravel 
free  from  clay  or  earth." 

MACADAM'S  METHOD. — Macadam  omitted  the  foundation  of 
large  stones,  claiming  that  it  was  not  only  useless  but  injurious. 
He  placed  on  the  natural  soil,  a  layer  of  stone  broken  into 
cubes  of  about  one  and  a  half  inches  in  their  greatest 
dimensions,  and  spread  equally  over  the  surface  of  the  road, 
to  a  depth  of  ten  or  twelve  inches. 


BROKEN-STONE  ROADS 


161 


No  binding  material  was  used,  the  stone  being  left  to  work 
in  and  unite  by  its  own  angles  under  the  traffic.     Macadam 
preferred  the  test  of  weight  to  that  of  measure- 
ment,   and    insisted   that   no   stone    should   weigh   Macadam>s 


method. 


more  than  six  ounces,  which  is  the  weight  of  a  cube 

of  one  and  a  half  inches  of  hard  compact  limestone,  arid  his 


7ft -* 


FIG.  115. — Modern  Telford  Road  as  Built  in  New  Jersey. 

overseers  were  provided  with  small  scales  and  a  six-ounce 
weight  to  test  the  larger  stones.  Macadam  was  the  pioneer 
of  scientific  road  construction  in  England,  but  he  had  been 
anticipated  in  the  promulgation  of  the  system  of  a  regularly 
broken-stone  covering  by  a  Mr.  Edgeworth,  an  Irish  proprietor 
who  wrote  a  treatise  on  roads,  early  in  the  nineteenth  century. 
This  contains  the  results  of  his  experiments  on  the  construction 


FIG.  116. — Modern  Telford  Road  in  Excavation 

Aid  Roads. 


Massachusetts  State- 


of  roads,  with  some  useful  rules,  in  which  he  advocated  the 
breaking  of  the  stone  to  a  small  size,  and  their  equal  distribu- 
tion over  the  surface,  also  that  the  interstices  should  be  filled 
with  small  gravel  or  sharp  sand — a  practice  which,  though 
condemned  by  Macadam,  is  now  advocated  by  the  best  road- 
makers. 

Modern  "  telford  "  consists  of  a  layer  of  stones  eight  inches 
thick,  set  by  hand,  on  a  natural-soil  bed,  properly  graded. 
These   are   arranged   and   wedged   as  described   by  M0(jern 
Telford.     On    this    stone    foundation,    a    layer    of  telford  and 
broken  stone  of  a  size  not  exceeding  three  inches  macadam. 
is  evenly  spread  and  rolled  and  this  surface  is  covered  with 


BROKEN-STONE  ROADS  163 

a  layer  of  sand  one-half  inch  thick,  and  the  rolling  continued. 
A  layer  of  stone  not  larger  than  two  inches  diameter  is  then 
spread  to  the  depth  of  four  inches  and  rolled,  followed  as 
before  with  a  layer  of  sand,  which  is  also  rolled.  Finally,  a 
coating  of  clean,  sharp  sand  is  applied,  well  watered,  and  the 
rolling  continued  until  the  surface  becomes  smooth. 

Modern  "  macadam  "  pavements  are  constructed  in  the  same 
manner  but  omitting  the  stone  foundation,  and  the  depth  of 
the  stone  varies  from  four  to  twelve  inches. 

The  principal  defects  of  the  telford  system  are: 

1.  The  large  percentage  of  voids  always  left  between  the 
foundation  stones,  giving  free  access  to  water  and  thus  defeat- 
ing one  of  the  main  objects  of  the  road  covering.      Defects  Of 

2.  The  crushing  of  the  smaller  surface  stones  on      telford 
the  harder  rock  of  the  foundation  by  the  traffic.  system. 

3.  The  high  cost  of  construction  due  to  the  stone  foundation. 

The  principal  defects  of  the  macadam  system,  when  con- 
structed as  directed  by  Macadam  is  the  looseness  of  the  layer 
of    broken    stones.     This    cannot    be    impervious,     j)efects  Of 
because  the  interstices  which  compose  a  considerable     macadam 
portion  of  the  bulk  of  loosely  spread  stones,  cannot     system, 
be  reduced  by  any  amount  of  rolling  more  than  one-fourth, 
leaving  a  space  that  will  be  filled  by  the  rising  of  the  sub- 
soil when  moistened.     The  lower  stones  are  then  forced  down 
by  the  weight  of  the  traffic  until  the  whole  becomes  a  mass  of 
mud  and  stones. 

The  advantages  of  broken-stone  pavements  are: 

1.  Good  foot-hold  for  horses. 

2.  Easy  traction  wrhen  in  good  condition.  and  Defects 

3.  Moderate  first  cost.  of  broken- 

4.  Comparative  noiselessness.  stone 
Defects  common  to  all  broken-stone  roads  are: 

1.  Muddy  when  wet  and  dusty  when  dry. 

2.  High  cost  of  maintenance. 

3.  Difficulty  in  cleaning. 

These  defects  prevent  the  use  of  broken  stone  for  city  streets, 
but  when  properly  constructed  and  maintained,  broken  stone 
forms  the  most  pleasant,  the  safest,  and  the  most  economic 


164  THE  ART  OF  ROADMAKING 

surface    for   suburban    streets    and    main    country    highways 
connecting  centers  of  population,  on  which  there  is  a  moderate 
volume  of  travel.     It  is  usually  too  expensive,  however,  for 
country  roads  other  than  the  main  ways. 
The  main  difficulties  in  the  construction   of    ideally  perfect 

broken-stone  roads  lie  in: 

Difficulties         \    The   quality   of   materials   suitable   for   road- 
making  found  in  different  localities. 

2.  The  conflicting  properties  possessed  by  these 
materials. 

3.  The  following  of  methods  of  construction  used  and 
precedents  established  under  entirely  different  conditions 
of  climate  and  traffic.  With  methods  of  construction  suitable 
to  local  conditions  and  with  a  thorough  knowledge  of  the 


FIG.  118. — Cross-section  of  Roadway  laid  on  Compact  Earth  and  Made 
Solid  and  Permanent  by  Rolling. 

nature  of  the  available  materials  under  any  given  conditions 
satisfactory  construction  of  broken-stone  roads  can  be  assured. 

The  essentials  requisite  to  the  successful  construction  of 
broken-stone  pavements  are: 

1.  The  removal  from  the  roadbed  of  all  vegetable  or  per- 
ishable matter. 

Essentials  2>  Tne  removal  of  the  natural  soil  to  such  a 
for  success-  depth  as  may  be  necessary  according  to  the  char- 

ful  construe-  acter  of  the  soil  and  the  thickness  of  the  intended 
tion. 

covering. 

3.  Thorough   sub-surface   drainage   wherever   required. 

4.  The  thorough  compacting  of  the  natural-soil  bed. 


BROKEN-STONE  ROADS  165 

5.  The  use  of  sand  or  gravel  for  the  foundation. 

6.  The  use  of  the  best  materials  available  either  locally  or 
imported  from  other  places,  according  to  the  nature  of  the 
traffic. 

7.  The  reduction  of  the  voids  in  the  mass  of  broken  stone 
to  the  least  possible  amount,  by  properly  proportioning  and 
distribution  of  the  different  sizes  of  stone  used. 

8.  The  complete  exclusion  of  clay  or  loam  from  the  broken 
stone. 

9.  The  use  of  sand  or  stone  dust  and  screenings  in  quantity 
sufficient  to  fill  the  voids. 

10.  The  thorough  compacting  of  the  broken  stone  with  a 
roller  of  sufficient  weight  and  suitable  form. 


FIG.  119. — Cross-section  showing  Wasteful  use  of  Material. 

Among  the  errors  in  broken-stone  road  construction  which 
make  the  road  very  unsatisfactory  and  defective,  are: 

1.  A  permeable   foundation   in  humid   climates.    Errors  in 

2.  The  use  of  excessively  hard  stones  which  can-    construe - 
not  be  consolidated  by  rolling.  tion* 

3.  The  use  of  improper  binding  material,  such  as  loam  and 
clay. 

4.  An  undue  proportion  of  soft  among  hard  stones. 

5.  Use  of  stones  of  too  large  size. 

6.  Use   of   stone   from   which  the   smaller  fragments  have 
been  excluded  by  screening.     Unscreened  stones  may  be  used 
for  the  lower  course,  but  its  use  for  the  surface  is  unsatisfactory, 
as  it  wears  unevenly,  and  owing  to  the  differences  in  the  size 
of  the  fragments,  the  variation  in  the  proportions,  and  their 
unequal  distribution  in  the  mass,  it  is  impossible  to  decrease 
the  amount  of  voids. 


166  THE  ART  OF  ROADMAKING 

7.  Laying  the  stone  in  layers,  according  to  the  size  of  the 
stone.     The  practice  of  building  up   a  road  with  strata  of 
screened  stone  assorted  in  different  sizes  and  growing  smaller 
towards  the  top  is  erroneous,  as  the  smaller  stone  will  sink 
to  the  bottom,  and  the  larger  stone  will  work  to  the  surface, 
making  the  road  porous  and  permitting  the  quick  formation 
of  ruts.     The  stone  should  be  assorted  by  screening  into  the 
several  sizes,  then  remixed  in  proper  proportions  to  produce 
a  mass  containing  the  least  possible  amount  of  voids  or  a  density 
as  nearly  equal  to  that  of  solid  rock  as  is  possible. 

8.  Covering  the   surface   of  the   compacted   stone   with   a 
layer  of  stone  dust. 

9.  Use  of  an  excessive  quantity  of  binding  material,  or  of 
water  when  rolling. 

As  stated  in  Chapter  VI,  the  materials  used  for  broken- 
stone  roads  must  necessarily  vary  according  to 
1  s*  the  locality,  and  on  account  of  the  many  differences 
in  climate  and  traffic  it  is  evident  that  no  single  material  is 
adaptable  to  all  cases.  As  in  practically  every  department 
of  engineering,  each  problem  requires  individual  solution 
according  to  local  conditions,  and  to  secure  the  best  results 
in  roadwork,  the  material  selected  and  the  method  of  con- 
struction employed  must  be  adapted  to  the  conditions  under 
which  the  road  is  to  be  used  and  maintained.  The  specifica- 
tions of  Telford  and  Macadam  were  drawn  up  for  use  in  a 
country  with  a  moist  climate.  The  water  was  useful  in  the 
construction  of  the  road  by  aiding  in  the  binding  together 
of  the  material,  but  its  removal  was  a  necessity  and  made 
drainage  of  both  the  roadbed  and  the  surface  an  important 
item  in  the  maintenance  of  the  road.  In  localities'  having 
little  or  no  rain,  drainage  becomes  relatively  unimportant, 
and  the  methods  for  preservation  of  a  well-bonded  surface 
are  of  great  consequence. 

-  For  ordinary  country  roads,  experience  has  shown  that  the 
broken-stone  way  need  not  be  more  than  from  12  to  15  feet 
wide,  if  suitable  shoulders  are  built  on  each  side.  Twelve  feet 
allows  two  vehicles  to  pass  each  other  safely.  Fifteen  feet 
allows  a  little  more  space  for  comfort,  particularly  when 


BROKEN-STONE  ROADS 


167 


Ancient  Roman  Road. 


Early  Eighteenth  Century  Road. 


Late  Eighteenth  Century  Road. 


Modern  Macadam  Road. 

(From  Judson's  "City  Roads  and  Pavements.") 
FIG.  120. — Relative  Thickness  of  Ancient  and  Modern  Roads. 


168  THE  ART  OF  ROADMAKING 

motor   vehicles   are   passing    each   other,    and   including   the 

shoulders,  this  width  will  permit  a  team  to  stand 
Dimensions  ,  M  .  .  ,  •  T/> 

of  the  beside  the  road  while  two  vehicles  are  passing.     If 

macadam  the  stone  is  less  than  12  feet  wide  there  is  a  likeli- 
surface.  no(xj  that  ^  ecjges  of  the  macadam  will  be  sheared 
off  by  the  wheels  unless  the  shoulders  are  made  of  especially 
good  material.  Whatever  maybe  the  width  of  the  stone,  the 
shoulders  should  be  firm  enough  to  permit  the  occasional 
passage  of  wheels  over  them. 

Until  within  comparatively  recent  years  it  has  been  almost 
universally  the  practice  to  build  thick  macadam  roads.  Roads 
less  than  8  inches  thick  were  rarely  heard  of,  and  often  a  thick- 
ness of  at  least  12  inches  of  macadam  was  thought  to  be  nec- 
essary for  good  work. 

The  modern  practice  is  to  make  the  macadam  surface  as 
thin  as  possible,  yet  with  sufficient  body  to  stay  in  place,  the 
theory  being  that  the  macadam  is  only  a  wearing  surface. 
By  lessening  the  thickness  of  the  macadam  much  expense 
may  be  saved,  since  the  foundation  materials  are  usually  less 
costly  than  broken  stone.  The  macadam  should  be  hard, 
smooth,  and  impervious  to  water.  Much  attention  must  be 
given  to  the  foundation.  It  should  be  composed  of  porous 
material  free  from  clay  or  loam,  firm,  and  sufficiently  strong 
to  sustain  any  load  likely  to  come  upon  the  road  at  any  time 
of  the  year. 

In  new  work,  where  no  macadam  has  been  laid  before,  3 
inches  of  macadam  after  rolling  is  the  least  thickness  which 
is  practicable,  and,  except  in  unusual  cases,  a  depth  greater 
than  6  inches  after  rolling  is  rarely  necessary  if  the  foundation 
is  suitable. 

The  ordinary  macadam  road  is  usually  from  12  to  16  feet 
wide,  with  shoulders  in  addition  3  to  5  feet  in  width  on  each 
side  of  the  broken  stone.  The  thickness  of  the  macadam  is 
usually  6  inches  at  the  center  and  4  inches  at  the  sides,  or  a 
uniform  depth  of  6  inches  throughout.  While  the  width  and 
depth  of  the  stone  are  often  less  than  these  dimensions,  only 
in  exceptional  cases  are  they  increased. 

The  actual  construction  of  the  road  consists  essentially  of 


OF    THE 

UNIVERSITY 

OF 


BROKEN-STONE  ROADS 


169 


three  operations:  (1)  The  preparation  of  the  subgrade,  or 
the  natural-soil  foundation  on  which  the  stone  is  placed; 
(2)  Spreading  of  stone;  (3)  Rolling  and  finishing. 

The  preparation  of  the  subgrade  to  enable  it  to  sustain  the 
superstructure  and  the  weights  brought  upon  it  requires  the 
observance  of  certain  precautions,  the  neglect  of 
which  will  sooner  or  later  result  in  the  deterioration 
or  possible  destruction  of  the  road  covering.     It  is  not  enough 


FIG.  121. — Cross-section  of  Sub-grade  as  Shaped  by  Grader. 

that  the  roadway  shall  be  graded  with  reasonable  care.  The 
surface  upon  which  the  broken  stones  are  to  be  placed  must 
be  hard,  smooth,  and  carefully  crowned.  If  the  foundation 
is  not  hard  and  firm  the  stones  will  be  pressed  into  it  by  the 
roller  and  wasted.  If  not  crowned,  an  unnecessary  quantity 
of  stone  will  be  used. 


FIG.  122. — Shaping  the  Subgrade  with  Road  Roller. 

Primarily  a  well-drained,  good  foundation  is  a  recognized 
necessity.  This  should  be  shaped  as  shown  in  Fig.  121.  Most  of 
the  dirt  to  be  moved  in  making  the  trench  for  the  broken  stone 
is  ploughed  and  thrown  out  with  an  ordinary  road  grader,  and 
the  trimming  up  to  the  lines  shown  in  Fig.  121  is  then  done 
by  hand.  The  trench  should  be  made  as  deep  at  the  sides  as 


170 


THE  ART  OF  ROADMAKING 


the  stone  is  to  be  after  rolling,  the  shoulders  being  made  two 
or  three  inches  higher  than  their  final  shape,  to  allow  for  their 
being  compacted  by  the  roller. 

When  the  roadbed  has  been  brought  to  shape,  the  trench 
is  thoroughly  rolled  until  it  is  hard  and  firm  and  shaped  as 
shown  in  Fig.  122.  Hollows  and  bumps  are  removed  by 
cutting  or  filling,  and  the  whole  subgrade  made  hard,  smooth 
and  even,  and  of  the  same  cross  slope  as  that  of  the  finished 
road.  After  the  trench  is  made  drains  should  be  cut  through 
the  shoulders  to  the  side  ditches  in  all  low  places  at  intervals 


FIG.  123. — Spreading  the  First  Course. 

of  50  feet  on  both  sides.  This  will  save  many  days'  work  in 
laying  stone,  as  it  will  keep  the  subgrade  dry  when  otherwise 
it  would  be  flooded  at  every  rain.  These  drains  should  be 
filled  with  the  three-inch  stone  when  the  stone  for  the  first 
course  is  spread;  they  then  serve  as  permanent  drains  for  the 
stone  roadbed  if  water  by  any  chance  gets  into  it. 

When  the   subgrade  has  been  thoroughly   rolled  the   first 
course  of  stone  is  spread.     This  ordinarily  consists 
of    stone    broken    to    sizes  varying    from  2  to   3J 
inches  and  need  not    be    of   especial   hardness  or 
toughness — ordinary  good  hard  stone  of  any  kind  may  be  used. 


First 
course 


BROKEN-STONE  ROADS 


171 


The  thickness  of  this  stone,  like  every  feature  of  the  road, 
varies  with  local  conditions.  On  good  soil  4  inches  loose  is 
sufficient,  but  in  some  cases  5  inches  and  even  6  inches  should 
be  used.  A  course  of  over  6  inches  cannot  be  thoroughly 
rolled  and  should  never  be  used.  Twelve  inches  of  stone 
loose  in  the  two  courses  is  all  that  is  ever  necessary  on  a  well- 
drained  road,  that  is,  two  courses  of  6  inches  each  without 
the  dust. 

It  is  often  specified  that  stone  for  any  course  should  not 
be  dumped  on  the  place  where  it  is  to  be  used ;  that  is,  that  after 
each  load  of  stone  is  dumped  it  should  be  raked  or  shoveled  into 
place,  moving  each  stone  from  the  place  it  was  dumped,  and 
thus  preventing  unevenness  in  the  road.  While  this  is  ad- 
vantageous, it  is  sometimes  impracticable  and  costly  to  have 


FIG.  124.— Rolling  the  First  Course. 

this  shoveling  and  raking  done,  especially  on  the  second  course 
of  stone,  and  good  results  are  obtained  by  taking  care  in 
raking  down  the  stone  from  the  pile.  Rolling  then  levels  all 
the  stone  to  a  uniform  thickness,  making  a  road  smooth  enough 
for  all  practical  purposes.  The  screenings,  however,  must  not 
be  dumped  directly  on  the  road  surface,  but  must  be  spread 
from  piles  or  directly  from  wagons. 

When  100  feet  or  more  of  stone  is  spread  and  shaped,  rolling 
is  commenced  and  is  carried  on  until  the  stone  is  thoroughly 
compacted. 

The  first  course  having  been  thoroughly  rolled,  the  second 
course  should  be  spread  the  same  width  as  the  first. 
This  course  should  consist  of  the  best  material 
economically  available;  which  means  the  material 
that  for  a  fixed  sum  will  produce  the  greatest  road  value,  not 
for  a  year,  but  for  twenty  years  or  more. 


Second 
course. 


172 


THE  ART  OF  ROADMAKING 


The  stone  should  be  broken  in  size  from  f  to  2  inches, 
and  be  screened  as  closely  as  possible  to  these  sizes.  It  should 
be  spread  to  a  depth  of  not  less  than  3  inches  nor  more  than 
5  inches  in  any  case,  varying  with  the  hardness  of  the  stone, 
etc.,  and  the  total  depth  of  road  desired.  This  course  must  be 
spread  with  the  same  care  as  the  first  course  and  rolled  in 
the  same  manner  until  the  stone  is  firmly  in  place  and  the 
whole  is  firm  and  even. 


Third 
course. 


FIG.  125. — Rolling  the  Second  Course. 

The  road  is  then  ready  for  the  third  or  binder  course,  which 
should  consist  of  stone  screenings  varying  from  dust  to  j-inch 
in  size.  It  is  usual  to  have  this  of  the  same  material 
as  the  second  course,  though  small  gravel  or  sand 
can  be  used  for  binder  for  some  rocks  with  good 
results.  The  dust  should  be  spread  with  shovels  from  the 
wagons  or  from  piles  alongside  the  road,  but  never  dumped 
directly  on  the  stone  surface.  It  should  be  applied  with  a 
quick,  jerky  motion,  so  that  a  shovelful  goes  over  a  large  area, 
until  the  second  course  of  stone  is  entirely  hidden  and  there 
is  a  uniform  coat  of  about  J  of  an  inch  over  the  whole  surface 
of  the  stone.  Then  the  road  should  be  rolled  as  before  until 
the  dust  is  well  pressed  into  the  space  between  the  stone  and 
a  coating  left  on  the  surface.  Bare  places  as  they  appear 
should  be  covered  with  more  screenings  until  the  whole  is 
firm  and  hard  and  none  of  the  second  course  stone  show. 

The  road  should  then  be  thoroughly  sprinkled  with  water 
from  an  ordinary  street  sprinkler  to  wash  the  screenings  into 
the  voids  in  the  stone,  and  when  it  flushes  or  rises  to  the  sur- 
face it  shows  that  the  voids  in  the  stone  have  been  filled. 
A  road  is  properly  flushed  when  the  steam  roller  following 


BROKEN-STONE  ROADS 


173 


close  behind  the  sprinkler  has  a  wave  of  water  continually 
going  before  the  wheels.  This  flushing  causes  the  dust  to 
settle,  and  bare  places  that  show  again  should  be  covered 
with  more  screenings  and  sprinkled  and  rolled  until  the  whole 
is  firm  and  hard,  and  uniformly  covered  with  a  thin  coat  of 
dust.  Just  enough  dust  should  be  applied  to  cover  the  stone 


FIG.  126. — Rolling  the  Binder. 


at  all  stages  of  the  finishing.  Too  much  dust  soon  ruts,  travel 
becomes  concentrated  in  these  ruts,  and  water  standing  in 
them  causes  a  soft  place  in  the  stone  below  and  the  ultimate 
destruction  of  what  would  otherwise  have  been  an  excellent 
road. 

After  a  section  of  road  has  been  flushed  and  finished  it 
should  be  closed  a  day  or  two  before  permitting  travel  upon  it; 
this  gives  the  road  an  opportunity  to  "dry  out  and  harden  and 
prevents  the  raveling  and  picking  up  of  the  road  surface  which 
sometimes  occurs  when  a  newly  finished  road  is  opened  too 
soon  and  in  too  wet  a  condition. 


a.  Method  of  Construction,  Showing  Curb  to  Prevent  Washing. 


TT 


b.  Road  Under  Water. 


c.  Completed  Road. 

FIG.  127. — Macadam  Road  Built  through  River  Bottom  (Auburn,  Neb.), 

174 


BROKEN-STONE  ROADS  175 

When  the  operations  outlined  above  are  about  finished  a 
road  machine  with  the  blade  set  to  the  proper  slope  should 
be  run  carefully  over  the  shoulders  and  all  surplus 
dirt  removed,  and  the  slope  from  the  center  of  the 
road  to  the  ditches  made  smooth  and  uniform  so  that  water 
falling  on  any  part  of  the  road  surface  is  quickly  carried  into 
the  ditches. 

The  broken-stone  road  of  to-day  is  quite  a  different  structure 
from  the  type  of  road  built  by  Macadam,  who  used  hand- 
broken  stone  that  was  practically  uniform  in  size,  laid  in  the 
road  without  the  addition  of  a  binder  of  stone  dust  or  sand  and 
left  to  be  compacted  by  passing  wheels.  Improvements  in 
methods  of  construction  have  reduced  the  thickness  from 
the  36  inches  of  the  Romans  to  the  18  inches  of  Telford,  to 
the  12  and  even  the  6  inches  of  Macadam,  to  the  6  and  in  some 
cases  the  4  inches  of  to-day;  the  chief  factors  being:  (1)  proper 
drainage  and  rolling  of  the  earth  foundation,  (2)  the  use  of 
machine-broken  and  screened  stone  with  the  screenings  for 
a  binder,  (3)  thorough  consolidation  with  a  steam  roller; 
and  it  is  safe  to  say  that  an  economic  road  cannot  be  built 
unless  all  of  these  factors  enter  into  its  construction. 

Efficient  rolling  is  a  matter  of  great  importance;  many 
roads  coated  with  material  of  good  quality  suffer  and  become 
loose  when  the  water  in  the  binding  has  dried  out. 
The  condition  to  be  aimed  at  is  to  solidify  the  coat- 
ing with  a  suitable  binding  applied  in  small  quantities  by  rolling 
so  as  to  approximate  the  original  bulk  occupied  by  the  material 
in  the  solid.  All  excess  binding  should  be  squeezed  out  by 
repeated  passages  of  the  roller  and  swept  off.  This  produces 
a  solid  crust  capable  of  resisting  most  effectually  the  action 
of  ordinary  wheel  traffic  and  containing  the  least  quantity 
of  soluble  matter  to  form  mud  in  wet,  and  dust  in  dry,  weather. 

The  non-professional  reader  may  have  wondered  why  a 
mass  of  broken  stone,  when  sprinkled  and  rolled,  finally  be- 
comes a  solid  pavement,  impervious  to  water,  acting  in  all 
respects  like  concrete,  although  no  cement  mortar  has  been 
used.  That  such  a  result  could  be  obtained  seems  not  to  have 
occurred  to  anyone  before  the  time  of  Tresaguet,  and  even  he 


176  THE  ART  OF  ROADMAKING 

did  not  trust  to  the  broken  stone  alone  to  sustain  loaded 
wagons,  for  he  used  an  underpinning  or  "bottoming"  of 
large  paving  stone.  It  was  Macadam  who,  by  omitting  the 
bottoming,  showed  conclusively  that  broken  stone  possesses 
the  property  of  knitting  together,  or  becoming  cemented 
under  the  rolling  action  of  passing  wheels,  but  it  is  doubtful 
if  Macadam  himself  understood  the  philosophy  of  this  cement- 
ing action. 

It  is  not  the  roller,  that,  by  shaking  and  pounding  a  mass 
of  loose,  broken  stones  placed  on  a  road,  finally  compresses 

the  stones  together  until  they  are  almost,  if  not 
What  holds  quite,  as  compact  as  solid  rock.  In  the  first  place, 
macadam  ^  ro^er  foes  not  compress  the  stone  to  its  original 
together.  volume,  that  is,  it  does  not  reduce  the  voids  to 

zero;  arid  secondly,  a  road  is  never  bound  when 
the  rolling  is  finished,  unless  a  binder  has  been  added.  The 
screenings  or  binding  materials  are  essential,  but  there  are 
various  views  as  to  their  action.  Mr.  H.  P.  Gillette  in  a  dis- 
cussion of  this  cementing  action,*  says: 

"A  true  explanation  of  the  phenomenon  seems  to  be  found 
in  a  study  of  the  sand  on  a  seabeach. 

"  Where  the  waves  break,  the  sand  is  firm  and  makes  a  very 
fair  road  itself,  while  a  little  farther  back,  beyond  the  reach 
of  the  waves,  the  sand  is  loose  and  yielding.  The  waves  have 
evidently  been  the  means  of  binding  the  sand. 

"  Each  wave  as  it  rushes  up  on  to  the  beach  carries  in  sus- 
pension an  amount  of  fine  sand  that  is  precipitated  upon  the 
surface  of  the  beach  where  the  wave  breaks  and  is  washed 
down  into  the  voids  of  the  larger  particles  of  sand,  thus  puddling 
or  filling  up  all  large  interstices;  but  there  is  one  more  nec- 
essary condition  to  secure  firmness  and  sustaining  power— 
the  sand  must  be  moist.  The  fine  capillary  pores  hold  the 
water,  or  rather  the  water  in  the  pores  holds  the  sand  together 
by  virtue  of  its  surface-tension,  a  well-known  physical  phenom- 
enon; and  it  is  this  surface-tension  or  viscosity  of  water  that 
binds  the  sand  together  and  makes  of  the  sand  beach  an  ex- 
cellent surface  to  walk  or  drive  over.  Strange  as  it  may  seem, 
dust  and  water,  commonly  considered  the  two  greatest  enemies 
of  good  roads,  are,  when  in  their  proper  places,  the  two 

*  "Economics  of  Road  Construction,"  p.  21. 


BROKEN-STONE  ROADS  177 

elements  that  prevent  the  disintegration  of  macadam.  The 
writer  conceives  that  macadam  is  first  bound,  not  by  cementing 
action,  but  by  the  surface-tension  of  water  on  the  capillary 
voids  of  the  screenings,  and  he  offers  the  following  facts  as 
evidence  of  the  truth  of  this  theory. 

1.  A  road  built  without  screenings  will  not  bind  unless  it  is 

left  long  enough  under  the  action  of  hoofs  and  wheels 
to  produce  screenings. 

2.  A  road  built  with  screenings  will  not  bind  if  all  the  dust 

has  been  taken  out  of  the  screenings,  leaving  only  the 
coarser  particles,  but  will  bind  immediately  upon  the 
addition  of  the  dust  and  water.  The  writer  has  tried 
this  experiment  under  the  direction  of  a  "good  roads 
expert"  who  had  ordered  all  the  dust  to  be  screened 
out,  under  the  mistaken  idea  that  it  would  be  injurious 
to  leave  it  in;  but,  as  stated,  it  was  found  impossible 
to  bind  the  road  until  the  dust  was  spread  over  its  sur- 
face and  washed  into  the  voids. 

3.  A  road  will  not  bind  until  sprinkled,  even  after  the  screen- 

ings or  binder  have  been  added. 

4.  Time  for  iron-rust  or  other  cementing  action  to  take  place 

is  not  necessary.  A  newly  bound  road,  one  that  can 
be  picked  to  pieces  without  evidence  of  any  cementa- 
tion, will  uphold  a  'heavy  wagon,  behaving  exactly 
like  an  old  road. 

5.  The  screenings  of  a  very  hard  rock  like  trap  bind  slowly, 

sometimes  not  at  all,  due  to  insufficiency  of  dust  nec- 
essary to  produce  capillary  voids;  but  upon  addition 
of  a  little  sand  or  road-sweepings,  bind  immediately. 
Conversely,  the  screenings  of  a  soft  rock,  like  lime- 
stone, rich  in  dust,  bind  quickly. 

6.  Hygroscopic  rocks  (those  that  condense  moisture  upon 

their  surfaces),  like  limestone,  furnish  better  screenings 
for  binding  and  do  not  ravel  as  quickly  in  dry  weather 
as  siliceous  or  quartz-like  rocks. 

7.  Long-continued  drought  causes    macadam   to  ravel  and 

finally  go  all  to  pieces,  while  it  immediately  knits 
together  again  after  a  rain. 

8.  Macadam  in  tunnels,  where   not  sprinkled,  soon  ravels, 

as  do  likewise  windswept  roads  that  are  kept  free  from 

sufficient  dust  and  moisture. 

"  The  writer  is  not  to  be  understood  as  advocating  the  use 
of  dust  and  water  alone  to  produce  binding,  rolling  being 
quite  as  important  a  factor,  if  a  road  is  desired  that  will  re- 
tain a  smooth  surface.  Rolling  in  the  first  place  so  con- 


178  THE  ART  OF  ROADMAKING 

solidates  the  stone  that  there  is  little  chance  for  play  or  move- 
ment, while  the  screenings  and  water  added  render  appreciable 
movement  impossible. 

"Sand  and  water,  or  screenings  and  water,  though  not  a 
true  mortar,  serve  the  same  purpose,  as  we  have  seen,  and  the 
less  mortar  in  any  masonry  structure  the  more  perfect  and 
durable  it  is." 

Steam  rollers  are  made  in  different  weights  and  used  accord- 


FIG.  128.— Steam  Roller. 

ing  to  the  condition  of  the  road  to  be  treated,  and  the  class  of 
material  employed  for  repairs.     Consideration  also 
rollers  must  be  given  in  regard  to  gas  and  water  mains 

and  other  pipes  under  the  roadway,  which,  in  many 
instances,  are  quite  near  the  surface,  or  have  but  a  limited 
cover.  The  weight  of  rollers  principally  used  are  12  to  15 
tons;  the  latter  is  mostly  employed  in  localities  where  the 
roadstones  are  hard  and  of  good  wearing  quality.  For  good 
country  roads  a  so-called  "  10-ton  roller"  is  sufficiently  heavy, 
as  most  of  the  culverts  and  many  of  the  bridges  are  too  weak 
to  sustain,  with  safety,  the  heavier  rollers.  The  prices  of  such 
rollers  range  from  $2500  to  $3500. 

Breaking  stone  for  road  purposes  was  formerly  clone  by  hand, 


BROKEN-STONE  ROADS  179 

but  since  the  invention  of  the  mechanical  stone  crusher  the 

cost  has  been  reduced  from  50  to  200  per  cent  and 

the  daily  output    has  been    increased   by  50  per 

cent.     In  some  European  countries,  however,  hand- 

broken  stone  is  still  preferred  on  the  ground  that  it  is  better 

broken  and  has  sharper  angles  than  that  broken  by  the  crusher, 

and  in  many  districts  the  occupation  affords  employment  for 

persons  who  would  otherwise  be  thrown  upon  the  public  for 

support. 

The  main  objections  to  machine-broken  stone  are: 

1.  Want  of  uniformity  in  size  of  stones. 

2.  The  stone  is  frequently  flaky  with  round  edges,  which 
is  a  very  disadvantageous  form  for  compacting. 

3.  Very  tough  stones  have  frequently  to  be  passed  several 
times  through  the  machine  before  they  are  properly  broken. 

4.  Very  soft  stone  are  crushed  to  powder. 

There  are  two  types  of  crushers  now  in  common  use:    the 
"Oscillatory"    (Fig.    129)    and   the    "Gyratory"    (Fig.    130). 
The  former  consists  of  a  strong  iron  frame,  near 
one  end  of  which  is  a  movable  jaw,  operated  back-       crushers 
ward  and  forward  a  slight  distance  by  means  of  a 
toggle-joint  and  an  eccentric.     As  the  jaw  recedes,  the  size 
of  the  opening  increases  and  the  stone  descends;    as  the  jaw 
again  approaches  the  frame,  the  stone  is  crushed,  the  size 
of  the  product  being  determined  by  the  distance  the  jaw  plates 
are  from  each  other  at  the  lower  edge. 

The  second  form  consists  of  a  solid  conical  iron  shaft  sup- 
ported within  a  heavy  iron  mass  shaped  somewhat  like  an 
inverted  bell.  In  the  pattern  shown  in  Fig.  130,  an  eccentric 
sleeve,  driven  by  a  removable  steel  gear,  rotates  around  a  sta- 
tionary central  shaft,  crowding  a  lined  crusher-head  outwardly 
along  horizontal  lines,  and  producing  the  stroke  which  causes 
the  stone  to  be  crushed  as  it  descends.  It  is  claimed  that  this 
form  has  an  advantage  over  the  "oscillatory"  in  that  no  time 
is  lost  in  crushing,  and  the  power  is  uniform  and  continuous. 

The  arrangement  of  the  plant  for  handling  and  crushing  the 
stone  is  very  important.  It  should  be  arranged  so  that  the 
stone  may  be  delivered  from  the  quarry  or  from  the  field  on  a 


180 


THE  ART  OF  ROADMAKING 


63    64 

FIG.  129.  —  Oscillatory  Crusher. 


66     67       68       69 


The  main  frame  (50),  a  solid  piece,  with  front  and  rear  inside  ends  planed  for  the 
seats  of  the  stationary  jaw  plate  (58)  and  the  removable  shims  (75).  (56)  is  the  steel 
swing  jaw,  having  a  jaw  seat  planed  for  the  jaw  plate  (55).  The  steel  pitman  (52)  is 
lined  with  babbitt,  and  means  of  taking  up  the  wear  of  bearing  is  effected  by  the  tapered 
keys  (74)  and  the  bottom  half  box  (54).  The  toggle  bearings  (62)  are  of  steel,  and  are 
held  in  position  by  means  of  wedge  blocks  (63). 


I 


(Courtesy  of  The  T.  L.  Smith  Co.) 


FIG.  130. — Gyratory  Crusher. 


BROKEN-STONE  ROADS  181 

level  with  the  mouth  of  the  crusher,  and  thus  save  lifting  the 
entire  product  and  throwing  it  into  the  machine.       stone- 
The  crushed  stone  should  be  elevated    to  bins  or       crushing 
pockets,  one  for  each  size,  so  arranged    as  to  dis-       plant, 
charge  directly  into  the  carts  or  wagons  that  haul  it  to  the 
road.     The  bins  should  have  a  considerable  capacity  so  as  to 
prevent  stoppage  of  the  machine  if  the  roads  are  too  bad  for 
hauling  or  if  for  any  other  reason  the  removal  of  the  crushed 
stone  is  delayed.     There  should  be  ample  room  around  the 
plant  to  prevent  the  interference  of  teams  coming  and  going. 

Revolving  screens  made  of  steel  plates  perforated  with  holes 
are  used  in  the  crushing  plant  to  separate  the  stone  into  the 
different  sizes  and  to  remove  the  tailings.  Dust  jackets  are 
used  in  connection  with  the  screens,  to  separate  the  dust  from 
the  crushed  stones. 

There  are  several  kinds  of  portable  plants  which  may  be 
bought  at  prices  ranging  from  $1600  to  $2500,  which  are 
admirably  adapted  for  country  use.  These  plants  include  the 
stone  crusher,  engine,  and  boiler,  portable  bins,  revolving- 
screen,  and  an  elevator  to  lift  the  stone  after  it  is  broken  and 
to  discharge  it  into  the  screen. 

The  outfits  are  mounted  on  wheels  and  may  be  moved  from 
place  to  place  at  a  comparatively  small  cost.  Under  ordinary 
conditions  from  $50  to  $100  will  pay  the  expense  of  shifting 
such  a  plant  from  its  old  location  to  a  new  location  several 
miles  distant. 

Stone  distributing  carts  (Fig.  133a)  are  specially  designed 
to  distribute  broken  stone  on  roads.  The  bottom  of  the  cart 
slopes  downward  to  the  back  and  the  tail-board 

is  hinged  at  its  upper  edge  and  is  furnished  with  Stone- 

,.      A.  .  .  ,  .  distributing 

two    adjusting   chains   by   which   the   opening   or   carts> 

swing  of  the  lower  edge  is  regulated.  Steel  wings 
are  attached  to  the  sides  of  the  cart  at  the  tail-board  for  the 
purpose  of  spreading  the  stone  the  full  width  between  the 
wheels.  The  cart  is  tilted  by  a  rack  and  pinion  operated  by 
the  driver  and  may  be  fixed  at  any  desired  angle.  As  the 
stone  flows  from  the  rear  of  the  cart  it  is  leveled  by  a  scraper 
attached  to  the  bottom  of  the  tail-board;  this  scraper  is  piv- 


182 


THE  ART  OF  ROADMAKING 


BROKEN-STONE   ROADS  183 

oted  at  the  center  and  can  be  adjusted  so  as  to  spread  the 
stone  to  any  required  thickness  and  over  any  desired  width 
equal  to  or  less  than  the  guage  of  the  cart,  and  thicker  on  one 
side  than  the  other. 

Scarifiers    (Fig.    13-4)    are   machines   or   mechanical   devices 
used     for   picking     or     breaking     up     of     broken- 
stone   roads  preparatory   to   the   applying   of  new 
road  material.     There  are  two  types;  one  fashioned  in  the  form 


FIG.  132.— Portable  Crushing  Plant. 

of  ploughs 'and  harrows,  and  the  other  based  on  the  principle 
of  the  rock  drill  or  ore-stamping  mill.  They  are  drawn  by 
horses  or  tractors.  The  shoe  is  usually  reversible  and  adjust- 
able, and  provided  with  a  sharp  and  blunt  point,  according 
to  the  class  of  work.  When  using  scarifiers,  it  is  essential 
to  have  the  road  thoroughly  soaked  with  water. 

The    Straight-edge,  or  Road   Level    (Fig.   135)   is   used  for 
obtaining  the   proper  transverse  form   of  roads.     It   consists 
of  a  horizontal  bar  having  in  the  center  of  its  length 
a    plummet    for    ascertaining    when    the    straight- 
cduc   is   level.      Adjustable   gauges  formed   of  up- 
right pieces  of  wood  marked  off  in  inches  are  placed  at  every 
four  feet. 

Since  water  is  always  needed  in  rolling  the  macadam,   a 


184 


THE  ART  OF  ROADMAKING 


FIG.  133a.— Stone  Distributing  Cart, 


.(Courtesy  of  Climax  Road  Machine  Co.) 

FIG.  1336.— Automatic  Distributing  Wagon. 


BROKEN-STONE  ROADS 


185 


watering   cart   or   sprinkler   should    be   provided.     The    road 

official   cannot  often    afford    to  wait    for    rain.     A 

cart  with  a    capacity  of   from  450   to    600   gallons 

will   be   sufficient.     Most   of   these   carts   are   pro-. 

vided  with  extremely  broad  tires,  so  that  the  cart  assists  in 


FIG.  134. — Scarifier. 


consolidating  the  stone,  instead  of  rutting  it.     Many  communi- 
ties are  provided  with  one  or   more  watering  carts,  so  that  it 
is  often  unnecessary  to  purchase  a  new  one  for  road  building. 
Comparisons  of  average  costs  of  roads  in  one  locality  with 


FIG.  135.— Straight-edge. 

those  in  another  are  of  little  instructive  value,  for  the  reason 

that  the  condition  in  the  two    localities    compared 

are   never  precisely   similar,   and  but   rarely  even 

approximately     alike.     Particularly     is     this     true      surfaces. 

of  such  details  as  earthwork  and  drainage.     Even 

the  costs   of   broken-stone   surfacings,  which  at   first  thought 


H 

bfi 

I 

Q 


BROKEN-STONE   ROADS 


187 


might  bex  considered  to  be  comparable,  one  locality  with 
another,  often  lead  to  wrong  conclusions.  There  are  too 
many  factors  which  are  dependent  on  local  conditions.  With 
this  caution,  certain  cost  data  of  macadam  work  alone  are 
given  below.  The  data  are  from  the  records  of  State  work 
in  Massachusetts  and  New  Jersey.  In  each  case  the  measure- 
ments and  costs  are  of  the  stone  in  place  and  rolled,  and  the 
lengths  and  costs  are  estimated  upon  the  basis  of  a  roadway 
15  feet  in  width.  Tables  ^K.  and  XI  relate  to  the  macadam 
work  alone  and  do  not  include  the  expenses  of  grading,  drainage 
or  any  other  incidental  items,  and  Table  XII  gives  the  average 
of  these  items  exclusive  of  macadam. 


TABLE  X 
AVERAGE   COSTS    OF   MACADAM    WORK   IN   MASSACHUSETTS 


Source 

Depth  of 
Stone  at 
Center. 
Inches. 

Depth  of 
Stone  at 
Sides. 
Inches. 

Total 
Distance 
Built. 
Miles. 

Cost 
?er 
Lie. 
Dollars. 

Cost  per 
Square 
Yard. 
Dollars. 

Cost  per 
Ton(2000 
Pounds). 
Dollars 

Imported  stone  (trap 
rock) 

/    6 
1    4 

4 
4 

8.25 
6  97 

5496 
4746 

0.6245 
0  5393 

1.956 

2  025 

Local  stone  

;  5 

4 

21.74 

3696 

0.4201 

1.396 

I    4 

4 

6.56 

3459 

0.3931 

1.583 

TABLE  XI 
AVERAGE   COSTS    OF   MACADAM   WORK   IN   NEW  JERSEY* 


Depth 
of  Stone. 

Total 
Distance 
Built. 

Cost  per 
Mile. 

Cost  per 
Square  Yard. 

Inches. 

Miles. 

Dollars. 

Dollars. 

4 

6.441 

2148 

0.2422 

5 

1.772 

3652 

0.4150 

6 

7.129 

5637 

0.6299 

8 

21.748 

6187 

0.6958 

*  Report  of  the  Commissioner  of  Public  Roads  of  New  Jersey  for  1905. 


188  THE  ART  OF  ROADMAKING 


TABLE  XII 

AVERAGES  OF  CONTRACT  PRICES  FOR  THE  SEVERAL 
CONSTRUCTION  ITEMS,  EXCLUSIVE  OF  MACADAM.— 
MASSACHUSETTS  HIGHWAY  COMMISSION 

Excavation per  cubic  yard $0.4352 

Borrow 0.5622 

Ledge  excavation 1 . 78 

€ement  concrete  masonry 8 . 85  * 

Shaping  road  for  broken  stone per  square  yard 0.281 

Vitrified  12-inch  clay  pipe,  in  place per  linear  foot 0.7662 

Vitrified  10-inch  clay  pipe,  in  place 0 . 6430 

Vitrified  8-inch  clay  pipe,  in  place 0 . 5700 

Vitrified  18-inch  clay  pipe,  in  place 1 . 57 

12-inch  iron  water  pipe,  in  place 2 . 20 

18-inch  iron  water  pipe,  in  place 3 . 75 

iStone  filling  for  V-drains,  in  place per  cubic  yard 0.8271 

Guard  rail,  in  place. per  linear  foot 0.2770 

Catch-basins,  in  place  (including  catch-basin  frames  and  grates) 

Each  35.74 

.Setting  stone  bounds 1 . 85 

*  This  price  does   not  include  the  cement  or   the   steel   reinforcement, 
which  may  be  estimated  at  about  $3  additional. 


CHAPTER   IX 
ROADS   IN   MOUNTAINOUS    DISTRICTS 

PROBABLY  the  greater  part  of  the  roads  in  mountainous 
districts  have  been  built  for  strictly  utilitarian  purposes;  in 
the  United  States  most  of  them  have  been  built  to  meet  a 
need  arising  in  some  way  from  the  existence  of 
mineral  deposits.  The  prospector,  with  his  tools,  Evolution  of 
blankets,  and  simple  food  packed  upon  his  burro,  roads 
goes  ahead;  for  him  neither  roads  nor  trails  are 
necessary  or  specially  desirable.  He  finds  the  mineral;  the 
news  gets  abroad,  and  at  once  others  flock  in  to  the  new]y 
explored  region.  Then  comes  the  trader  with  supplies,  men 
to  buy  the  mineral  output,  and  miners  to  work  the  new  finds. 
The  freighter  writfi  his  mule  teams  furnishes  transportation, 
and  for  his  use  are  built  the  first  mountain  roads.  The  first 
desideratum  seems  to  be  a  route  over  which  vehicles  on  four 
wheels  can  travel  without  tipping  over.  It  is  often  so  steep 
in  places  that  wagons  can  only  be  pulled  up  with  blocks  and 
tackle,  and  descend  with  wheels  rough  locked  and  dragging 
a  heavy  log  behind. 

Next  come  roads  to  particular  mines,  toll  roads,  county  and 
State  roads,  usually  of  such  bad  construction  that  it  may  be 
truthfully  said  that  the  money  squandered  in  traveling  over 
them  would,  in  five  years  or  less,  build  new  ones  intelligently 
located  and  properly  constructed.  Such  roads  would  make 
available  vast  deposits  of  minerals  now  lying  idle,  furnishing 
new  markets  for  labor,  mining  machinery,  and  farm  products, 
and  benefiting  directly  or  indirectly  every  industrial  and 
financial  enterprise  in  the  country. 

But  mountain  roads  must  not  be  considered  alone  from  an 
industrial  standpoint — the  inspiring,  health-giving  effects  of 
mountain  air  and  mountain  scenery  are  universally  conceded 

189 


190 


THE  ART  OF  ROADMAKING 


FIG.  137.— The  Mesa  and  Roosevelt  Stage  Road,  Salt  River  Project, 

Arizona. 


ROADS  IN  MOUNTAINOUS  DISTRICTS  191 

and  for  both  those  living  in  them,  and  those  who  come  to  them 
for  business,  pleasure,  or  health,  the  need  for  roads  which  can 
be  traveled  in  safety  and  comfort  is  just  as  imperative  as  it 
is  elsewhere.  The  sentiment  which  demands  good  roads  is 
increasing  steadily  and  will  not  halt  at  the  foot  of  the  moun- 
tains. 

The  location  and  construction  of  roads  in  mountainous 
countries  present  greater  difficulties  than  in  an  ordinary 
undulating  country.  The  most  important  consideration  is 
grade.  As  stated  in  Chapter  I  for  freight  traffic  the  maximum 
grade  admissible  is  12  per  cent.  Four  animals, 
together  with  the  wagons  used  on  a  mountain 
road,  are  all  that  one  driver  can  safely  and  properly  handle 
on  steep  grades.  When  he  uses  two  wagons,  lead  and  trail, 
at  every  stop  ascending  he  must  hold  both  wagons  by  the 
brakes  on  the  lead;  in  descending  with  heavy  loads,  he  must 
control  his  wagons  with  brakes  on  both  and  when  the  road  is 
icy  he  must  control  the  descent  by  rough-locking  one  or  more  of 
his  rear  wheels.  To  do  this,  he  attaches  some  rough  device, 
like  a  piece  of  chain,  or  a  short  steel  runner,  grooved  on  the 
upper  side  to  fit  the  tire  and  with  projecting  prongs  on  the 
lower,  to  the  rear  wheel,  and  a  chain  attached  firmly  to  the 
center  of  the  forward  axle  is  then  tightly  fastened  to  this 
rough-lock.  Thus  secured,  as  the  wagon  descends  the  hill, 
the  wheel  remains  rigid  and  the  rough-lock  plows  into  the 
surface  of  the  road. 

Experience  in  heavy  freighting  has  shown  that  wagons  can 
be  actually  and  satisfactorily  controlled  in  all  weathers  on 
12  per  cent  grades,  .but  that  they  can  not  be  thus  controlled 
on  steeper  grades,  and  that  where  much  heavy  freighting  has 
been  attempted  on  steeper  grades  it  has  almost  invariably 
been  attended  with  terrible  accidents.  On  a  properly  con- 
structed dry  road  four  animals,  averaging  1300  pounds  each  in 
weight,  will  haul  6500  pounds,  total  weight,  distributed 
between  wagons  and  contents,  up  a  12  per  cent  grade,  at  the 
rate  of  about  1^  miles  per  hour.  Descending,  the  four  animals 
will  haul  all  that  a  wagon  can  hold  up,  but  in  practice  this 
amount  rarely  exceeds  16,000  pounds  on  a  single  wagon  or 


192 


THE  ART  OF  ROADMAKING 


FIG.  138.— Ute  Pass,  Colorado. 


FIG.  139. — Ouray  and  Silver-ton 
Toll  Road,  Colorado. 


ROADS  JN  MOUNTAINOUS  DISTRICTS  193 

20,000  pounds  on  a  lead  and  trail,  and  the  average  is  probably 
about  10,000  pounds  or  14,000  pounds. 

Mountain  roads  are  routes  of  travel  between  points  of 
different  altitudes  and  the  most  common,  as  well  as  the  most 
serious,  mistake  made  in  their  location  is  the  attempt  to 
cover  this  distance  by  too  short  a  line.  On  a  12  per  cent  grade 
every  pound  of  freight  going  up  is  elevated  12  feet  for  each 
100  feet  of  horizontal  distance  traveled.  On  an  8  per  cent 
grade  it  is  elevated  12  feet  in  150  feet  of  horizontal  distance 
traveled,  while  on  a  6  per  cent  grade  it  is  elevated  the  same 
amount  in  200  feet  of  horizontal  distance;  or,  in  other  words, 
the  distance  required  to  get  a  12  per  cent  grade  must  be 
increased  one-half  for  an  8  per  cent  grade  and  doubled  for  a 
6  per  cent  grade.  The  limit  of  load  which  a  team  can  pull 
on  any  road  is  determined  by  the  steepest  place  in  that  road, 
and  it  is  putting  it  very  moderately  to  say  that  a  team  will 
haul  up  50  per  cent  more  load  in  the  same  time  between  two 
given  points  on  a  road  with  an  8  per  cent  maximum  than  it 
could  haul  on  one  of  similar  surface  with  a  12  per  cent  maximum. 
A  12  per  cent  grade  is  admissible  as  a  maximum  and  it  is 
rare  that  a  mountain  road  is  built  with  a  less  maximum  gradient, 
but  it  is  also  true  that  there  are  very  few  places  where  it  was 
not  feasible  to  secure  a  maximum  under  this,  and  the  extra 
length  that  would  be  required  is  generally  much  less  than 
might  at  first  be  supposed. 

Besides  the  advantage  in  upfreighting,  the  8  per  cent  road 
is  vastly  safer  for  both  light  driving  and  freighting;  on 
passenger  vehicles  brakes,  while  desirable,  are  not  essential  to' 
safety;  with  heavy  loads,  if  the  brake  fails,  there  is  a  fair 
chance  of  escape  for  driver,  team,  and  wagon.  Such  a  road 
is  not  seriously  damaged  by  rain  and  melting  snows,  which 
work  much  injury  on  steeper  grades;  damage  from  rough 
locking  is  enormously  reduced,  and  as  such  practice  can  be 
to  a  great  extent  avoided,  the  time  thus  consumed  is  saved. 
Repair  bills  on  wagons  and  harness  are  lessened,  and  the  life 
of  wagons  is  greatly  prolonged.  It  is  a  pleasure  to  drive 
down  an  8  per  cent  grade,  but  as  gradients  become  steeper 
the  sense  of  danger  grows  more  and  more  keen.  As  a  rule,  a 


194 


THE  ART  OF  ROADMAKING 


lower  gradient  than  8  per  cent  means  too  long  a  route  without 
commensurate  advantage,  while  a  higher  means  an  unnecessary 
loss  in  the  very  purpose  for  which  a  road  is  required.  The 
maximum  adopted  in  the  old  Government  pike  crossing  the 
Alleghenies  was  7  per  cent. 

Next  in  importance  to  grade  is  location.  The  worst  obstacle 
encountered  on  mountain  roads  is  snow.  The  snow  slide,  or 
avalanche,  comes  sweeping  down  the  mountain  side,  carrying 
along  everything  it  meets  and  depositing  its  accumulations 


Courtesy  of  The  Literary  Digest. 

FIG.  140. — The  Devil's  Elbow,  Isle  of  Wight. 

when  the  momentum  is  exhausted.     The  customary  routes  of 

these   slides   are  generally   quite   apparent  to   the 

mpor  ance   mountaineer,  and  in  laying  out  a  mountain  road, 

they  can  be  avoided  by  crossing  to  the  farther  side 

of  the  gulch  and  placing  the  line  so  high  that  the  snow  slide 

will  always  stop  beneath  it.     If  a  snow  slide  covers  a  road  it 

is  rarely  practicable  to  clear  it  for  heavy  traffic  for  months. 

The  accumulation  of  ice,  snow,  rocks,  trees,  and  debris  of  all 

kinds  is  so  enormous,  and  the  cost  of  removing  it  during  the 

cold,  short  days  of  winter  so  excessive  that  a  snow  slide  generally 

remains  where  it  falls  until  warm  w.ather  aids  in  its  removal. 


ROADS  IN  MOUNTAINOUS  DISTRICTS  195 

In  roads  designed  for  heavy  traffic,  it  is  the  wisest  economy  to 
avoid  snow  slides  at  almost  any  cost. 

Next  to  snow  slides  in  obstructive  effect  are  snowdrifts. 
These  are  due  to  air  currents  and  act  with  remarkable  uni- 
formity from  year  to  year.  The  places  where  these  drifts 
accumulate  in  excessive  amount  can  generally  be  located 
and  avoided  by  careful  attention.  Deep  ravines  almost 
always  catch  snow.  In  a  snow  region  it  always  pays  to  go 
around  a  point  by  a  sidehill  grade  in  preference  to  cutting 
through  it. 

Roads  should  always  be  located  on  slopes  facing  south  and 
east  in  preference  to  slopes  facing  north  and  west,  as  they 
afford  the  sun  greater  power  to  settle  and  melt  the  snow. 

Very  steep  sidehill  slopes  and  hard  rock  increase  the  cost  of 
road  building,  but  it  is  often  possible  to  avoid  them  to  a  greater 
or  less  extent.  In  fact,  many  of  the  problems  in  road  location 
that  at  first  seem  impossible  of  practicable  solution  can  be 
solved  by  observation  and  study.  Thousands  of  miles  of 
mountain  railroad  have  been  replaced  at  enormous  cost, 
because  of  mistakes  in  original  location,  which  more  intelligent 
study  would  have  avoided,  and  the  same  principle  applies  in 
road  building. 

In  level  regions  roads  are  drained  to  protect  their  foundations ; 
in  the  mountains  they  are  drained  principally  to  protect  the 
surface.  Water  naturally  runs  off  from  a  slope, 
and  in  doing  so  it  must  always  leave  more  or  less  9b-'.ect  of 
effect.  Every  mountain  road  must  run  through  a 
valley  or  along  a  hillside.  If  in  a  valley,  the  surface  should 
have  a  crown  of  at  least  6  inches,  with  gutters  and  ditches 
and  drains  just  as  in  properly  constructed  roads  in  a  level 
region.  In  mountain  roads  on  hillsides,  the  outside  of  the 
road  must  be  the  highest,  with  the  view  of  conducting  the 
water  as  quickly  as  possible  towards  the  inside  bank,  where 
it  should  find  a  gutter  to  carry  it  to  the  nearest  drain.  This 
prevents  the  water  from  spilling  over  and  washing  away  the 
outside  bank,  and  also  has  a  tendency  to  keep  it  from  running 
down  in  the  ruts  and  enlarging  them.  Another  reason  for 
keeping  the  outside  of  the  road  on  hillside  grades  higher  than 


196  THE  ART  OF  ROADMAKTNG 

the  inside  is  that  there  is  always  a  tendency  for  the  wheels  of 
a  heavily  loaded  wagon  to  slew  toward  the  lower  side,  which 
becomes  very  serious  when  the  road  surface  is  slippery,  and 
terrible  accidents  have  resulted.  Rain  or  melting  snow 
always  wears  down  some  of  the  material  from  the  inside  bank. 
If  the  road  surface  slopes  outward,  this  debris  follows  the 
drainage  across  the  road,  continually  increasing  the  slope, 
sometimes  very  rapidly  in  cold  weather;  hence,  the  roadbed, 
for  the  protection  both  of  the  bed  and  the  traffic,  should  be 
constructed  and  maintained  with  an  inward  slope  of  at  least 
one-half  inch  to  the  foot.  The  inside  gutter  should  empty 
into  drains  crossing  the  roadbed  diagonally  at  suitable  intervals, 
determined  by  the  amount  of  drainage. 

The  importance  of  batter  *  in  mountain  road  building  is 
almost  universally  ignored.     It  is  very  common  to  see  hill- 
side grades  constructed  with  an  insecure  vertical 
Necessity  for  cribbing  constituting  the  outside  of  the  roadbed ; 
slope"  ^e  mgide  bank  cut  as  nearly  vertical  as  possible, 

and  three-quarters  of  the  entire  width  of  the  road 
perhaps  built  of  material  .filled  in,  the  filling  generally  including 
all  the  trash  available  (boughs,  sticks,  boulders,  etc.),  with  a 
covering  of  such  material  as  the  bank  affords ;  and  of  insufficient 
width,  to  hold  a  wagon  when  the  road  is  first  built.  The 
destructive  forces  of  nature  act  vigorously  on  such  a  roadbed 
from  the  start.  Ice  and  water  rapidly  wear  down  the  inside 
bank,  and  the  debris  falls  upon  the  roadbed;  the  trash  founda- 
tion settles  and  the  road  sinks,  sloping  outward;  water  finds 
its  way  through  this  loose  material  and  undermines  the  roadbed. 
The  cribbing  settles,  rots,  and  soon  disappears  altogether  and 
unless  the  road  is  practically  rebuilt  in  a  few  years  it  grows 
more  and  more  dangerous,  and  finally  becomes  absolutely 
impassable. 

Cribbing  is  temporary  in  character,  its  use  costly,  and 
always  to  be  avoided  wherever  practicable;  when  indispensable, 
it  should  have  a  batter  not  steeper  than  one  horizontal  to 
four  vertical.  Roads  excavated  in  solid  rock  should  have 

*  The  side  slope  of  a  cut,  embankment,  or  wall. 


ROADS  IN  MOUNTAINOUS  DISTRICTS  197 

an  inside  batter  of  one  horizontal  to  four  vertical,  which  affords 
some  latitude  for  projecting  loads. 

Cost,  amount  of  traffic,  safety,  and  comfort  are  the  factors 
which  must  determine  the  width  of  a  wagon  road.     Comfort 
and    convenience    are    of    course    promoted    by    a 
double  track;    extensive  traffic  demands  it;    safety 
requires  so  much  of  it  that  teams  can  pass  and  never  be  caught 
unawares  on  a  single  track. 

The  proper  width  for  double  track  and  heavy  teams  is  16 
feet,  while  it  is  possible  for  them  to  pass  with  extra  caution  on 
a  14-foot  track  on  a  straight  road.  For  single  track  and 
greatest  safety  a  desirable  width  is  12  feet,  while  10  feet  is 
generally  safe,  and  an  8-foot  roadbed  can  be  driven  over  if 
the  inside  bank  has  sufficient  batter,  so  that  vehicles  will  not 
be  crowded  off. 

Double  tracks  for  turnouts  should  never  be  less  than  75  feet 
long.  These  should  be  visible  from  each  other  and  from  every 
foot  of  the  intervening  distance.  Before  laying  out  a  road, 
the  maximum  distance  between  turnouts  should  be  determined 
from  all  the  conditions,  especial  consideration  being  given 
to  the  amount  of  travel  likely  to  occur  at  night,  and  this 
maximum  should  never  be  exceeded.  Where  this  maximum 
is  over  100  feet  for  turnouts  adapted  to  heavy  traffic,  the  road 
should  be  widened  for  short  distances  at  intervening  intervals, 
for  light  vehicles.  A  width  of  12  feet  will  allow  light  vehicles 
to  pass  each  other  in  an  emergency  and  where  the  utmost 
economy  must  be  observed,  this  extra  width  for  a  short 
turnout  can  often  be  secured  by  cutting  into  the  bank.  If 
this  has  been  constructed  with  proper  batter,  the  cutting 
makes  the  inside  bank  too  steep  at  the  turnout,  but  it  is  a 
choice  of  evils  in  the  interest  of  greater  convenience  and 
safety  to  light  traffic. 

It  is  obvious  that  in  sidehill  grades  excavated  in  easy  ground, 
that  portion  of  the  road  that  is  formed  from  the  original 
material  in  place  must  for  a  time  be  more  solid  than  the 
portion  built  out.  It  is  consequently  desirable  on  roads 
designed  for  very  heavy  traffic  that  all  the  wheels  of  heavily 
loaded  wagons  should  rest  upon  the  original  solid  formation. 


198 


THE  ART  OF  ROADMAKING 


Standard  vehicles  are  either  4  feet  6  inches,  or  5  feet  between 
centers  of  tires.  A  very  heavily  loaded  wagon  can  not  be 
restricted  to  the  same  width  of  roadbed  as  light  vehicles,  but 


FIG.  141. 

should  be  allowed  a  latitude  of  8  feet  for  varying  conditions 
of  draft,  road  surface,  etc. 

TABLE  XIII 

WIDTHS  OF  ROADBED  FOR  VARIOUS  SIDEHILL  SLOPES, 
WITH  AMOUNT  OF  MATERIAL  EXCAVATED  PER  100 
FEET 


Sidehill 
Slope 
(cad), 

Width  Made  by  Fill  (eo), 
Feet. 

Total  Width  (eb), 
Feet. 

Excavation  per  100 
Feet,  Cubic  Yards. 

Deg. 

8-ft. 

6-ft. 

5-ft. 

8-ft. 

6-ft. 

5-ft. 

8-ft, 

6-ft, 

5-ft. 

Cut. 

Cut. 

Cut. 

Cut. 

Cut. 

Cut. 

Cut. 

Cut. 

Cut. 

5 

7.89 

5.92 

4.93 

15.89 

11.92 

9.93 

11.26 

6.33 

4.40 

10 

7.83 

5.87 

4.89 

15.83 

11.87 

9.89 

25.33 

14.25 

9.97 

15 

7.72 

5.79 

4.83 

15.72 

11.79 

9.83 

43.41 

24.41 

16.96 

20 

7.52 

5.64 

4.70 

15.52 

11.64 

9.70 

67.41 

37.89 

26.33 

25 

7.29 

5.47 

4.56 

15.29 

11.47 

9.56 

103.41 

58.15 

40.41 

30 

6.87 

5.15 

4.30 

14.87 

11.15 

9.30 

161.78 

91.0 

63.19 

35 

5.94 

4.45 

3.71 

13.94 

10.45 

8.71 

276  .  59 

155.59  108.06 

A  hillside  composed  of  picking  or  plowing  ground  is  rarely 
ever  steeper  than  35°  and  a  grade  formed  by  cutting  8  feet 
into  such  material  makes  an  excellent  road.  The  inside 


ROADS  IN  MOUNTAINOUS  DISTRICTS  199 

8  feet  of  it  is  solid  and  adapted  to  the  heavest  traffic,  and  the 
balance,  made  by  the  fill,  is  sufficiently  wide  to  allow  lighter 
wagons  to  pass.  The  following  table  shows  the  total  width 
of  roadbeds  for  various  sidehill  slopes  and  the  amount  of 
material  which  must  be  excavated  for  each  100  feet  of  roadbed 
for  8-,  6-  and  5-foot  cuts  into  plowing  or  picking  ground. 

From  these  tables  it  will  be  seen  that  while  there  should  be 
a  cut  of  8  feet  into  the  bank  for  a  double-track. road,  a  cut  of 
5  feet  will  give  a  practical  single-track  road  with  only  ff  as 
much  excavation,  or  that  the  double-track  road  requires  more 
than  two  and  one-half  times  as  much  excavation  as  a  single 
track. 

In  sidehill  grades  in  rock  the  conditions  are  very  different. 


FIG.  142. 

Rock  excavations  are  made  by  blasting,  which  throws  a  large 
proportion  of  the  rock  down  the  hill,  and  consequently  the 
material  thus  broken  out  can  not  be  depended  on  with  any 
certainty  for  fill.  That  which  does  remain  available  increases 
in  bulk  about  50  per  cent. 

When  the  natural  surface  of  the  rock  is  too  steep  to  hold 
a  fill  it  is  often  the  better  practice  to  cut  the  entire  roadbed 
out  of  the  solid  rock  as  in  Fig.  142.  Such  a  roadbed  is  absolutely 
secure  and  in  no  danger  of  giving  way  without  warning, 
through  the  failure  of  cribbing  or  retaining  walls.  For  a 
single  track  this  roadbed  should  be  10  feet  wide,  carefully 
protected  on  the  outside  by  a  guard  log  firmly  bolted  to  the 
rock.  The  amount  of  excavation  in  solid  rock  on  different 
hillside  slopes  to  obtain  such  a  roadbed  is  shown  in  the  follow- 
ing table,  which  can  be  used  for  deeper  cuts  by  using  the 
rule  that  the  amount  of  material  varies  as  the  square  of  the 


200 


THE  ART  OF  ROADMAKING 


depth  of  the  cut.     For  instance,  an  11 -foot  cut  will  require 
the  excavation  shown  in  the  table;  a  12-foot  cut,  }-££,  etc. 

TABLE  XIV 

AMOUNT    OF    EXCAVATION    IN     10-FOOT    CUT    INTO    SOLID 

ROCK 


Sidehill  Slope 
(bad).     Degrees. 

Excavation  per  100 
Feet.     Cubic  Yards,   i 

Sidehill  Slope 
(bad).      Degrees. 

Excavation  per  100 
Feet.     Cubic  Yards. 

5 

16.30 

25 

97.78 

10 

34.07 

30 

125.19 

15 

53.33 

35 

157.04 

20 

74.07 

40 

196.30 

Curves. 


The  minimum  curve  allowable  on  mountain  roads  has  the 
arc  of  a  circle  with  a  30-foot  radius  for  its  outer  edge.  All 
sharp  curves  and  their  approaches  from  each  direc- 
tion should  be  level,  a  principle  of  great  importance 
to  the  efficiency  and  safety  of  mountain  roads. 

Where  a  road  zig-zags  backward  and  forward  up  a  hill  in 
approximately  parallel  lines  the  turns  are  called  switchbacks. 
They  are  expensive  and  very  undesirable,  and  where  possible, 
they  should  be  avoided. 

Wherever  a  bridge  is  approached  by  a  .curve  its  end  should 
be  flaring  and  the  roadbed  made  wide  and  level,  as  curved 
approaches  to  bridge  are  very  undesirable  and  should  be 
avoided  if  practicable. 

In  the  mountains  the  hillside  slopes  are  often  covered  with 
broken  stone  of  various  sizes,  called  "  slide  rock."  This  slide 
rock  may  be  very  coarse  and  the  surface  extremely 
ragged,  when  it  is  called  " heavy  slide";  it  may  be 
fine  and  bound  together  by  soil,  in  which  case  it  can  be  plowed 
or  it  may  be  fine  and  dry  and  run  just  like  dry  sand  when 
disturbed,  when  it  is  called  "fine  slide  rock."  To  construct  a 
road  in  coarse  slide  a  retaining  wall  is  built  on  the  outside  of 
the  grade,  of  large  rocks  weighing  not  less  than  75  pounds 
each.  The  roadbed  is  then  made  as  smooth  as  possible  with 
the  material  at  hand,  and  covered  with  fine  slide.  Coarse  and 


Slide  rock. 


ROADS  IN  MOUNTAINOUS  DISTRICTS  201 

rough  heavy  slide  may  give  the  very  best  results  when  care- 
fully handled,  furnishing  an  absolutely  solid,  perfectly  drained 
road  foundation,  unaffected  by  the  elements,  and  requiring 
less  outlay  for  repairs  than  any  other  variety  of  mountain 
road. 

Probably  the  most  difficult  material  which  the  mountain  road 
builder  encounters  is  fine  slide  rock ;  it  appears  to  be  so  utterly 
unstable  in  every  way  that  it  seems  impossible  to  obtain 
cither  definite  or  satisfactory  results.  It  cannot  be  plowed 
or  scraped  and  neither  man  nor  animal  can  keep  a  footing  in 
it,  but  fortunately,  such  patches  arc  never  very  long,  and 
while  the  process  of  making  a  road  across  it  is  tedious  and 
expensive,  it  can  always  be  successfully  accomplished. 

In   laying   out   mountain   roads   a   spongy   soil  filled   with 
water  is  often  encountered  which  almost  invariably  proves 
to   be   shallow,   with   a  substratum   of  good  road 
material.     This  surface  soil  must  be  removed  and 
a  system  of  drainage  adopted  to  keep  surface  water  from 
running   onto   the   roadbed.     Occasionally   corduroy   is   used 
to  meet  such  conditions,  but  it  is  a  very  undesirable  expedient, 
and  is  adopted  only  in  extreme  cases. 

A  thorough  system  of  both  cross  and  longitudinal  drainage 
must  be  adopted  to  protect  the  corduroy  from  quickly  rotting 
and  to  keep  its  foundation  from  settling  unevenly. 

As  all  mountains  are  made  of  rock,  the  soil  with  which  they 
are  in  places  covered  being  merely  a  product  of  rock  decom- 
position and  water  concentration,  a  rock  dressing 
prepared  by  nature  can  generally  be  found  within 
convenient  distance   of  a  mountain  road.     A  hard  rock  in 
angular  fragments  of  two  inches  or  less  diameter  makes  an 
excellent  road  covering  if  some  suitable  fine  material  is  put 
on  top  of  it.     Sometimes  it  is  best  to  mix  two  kinds  of  rock, 
one   hard    and    durable    and   the   other   disintegrating   more 
rapidly  through  wear  and  chemical  decomposition. 

Most  mountain  roads  at  first  require  dressing  only  in  stretches, 
and  later  for  repairing  holes  and  ruts  and  for  maintaining  a 
suitable  inward  slope.  With  a  covering  of  3  inches,  600  tons 
of  rock  dressing  will  completely  cover  a  full  mile  of  single- 


202  THE  ART  OF  ROADMAKING 

track  road,  and  on  the  average  mountain  road  that  amount 
would  be  sufficient  for  2  miles. 

As  in  all  broken  stone  roads  if  the  surface  is  to  wear  evenly, 
it  should  be  homogeneous,  and  not  built  or  repaired  in  spots 
with  different  kinds  of  materials;  a  clay  road  should  not  be 
patched  with  gravel  nor  a  gravel  road  with  clay.  Holes  or 
ruts  should  be  filled  with  material  of  the  same  kind  as  con- 
stitutes the  road  surface.  Detritus,  resulting  from  traffic, 
which  is  washed  by  rains  into  the  gutters,  should  not  be  placed 
back  upon  the  surface,  for  it  has  lost  its  power  of  cementation; 
it  should  be  thrown  away  and  replaced  by  fresh  material. 


CHAPTER  X 

IMPROVEMENT    AND    MAINTENANCE    OF    COUNTRY    ROADS 
RECONSTRUCTION  AND  IMPROVEMENT 

THE  reconstruction  or  improvement  of  existing  roads  is 
chiefly  a  question  relating  to  the  waste  of  effort  and  the  sav- 
ing of  expense.  Good  roads  reduce  the  tractive  resistance  of 
loads,  and  consequently  the  cost  of  moving  the  load. 

The  financial  value  of  the  benefits  of  a  proposed  improve- 
ment must  be  carefully  estimated  before  any  work  is  under- 
taken and  this  value  must  be  ascertained  for  each  portion  of 
the  road.  To  obtain  this  the  following  data  are  required: 

1.  The  quantity  and  quality  of  the  traffic  using  the  road. 

2.  The  cost  of  haulage. 

3.  Plan  and  profile  of  the  road. 

4.  Character  and  cost  of  the  proposed  improvement. 

The  defects  of  existing  roads  are  generally:    (1)  unnecessary 
ascents  and  descents;    (2)  unnecessary  length;    (3)  imperfect 
surface;     and   the   improvement   may   be    divided 
into  three  branches :  Defects  of 

1.  Rectification   of   alignment   and   grades,    con- 
sisting  of   the    application    of    the    principles    laid 

down  for  the  location,  etc.,  of  new  roads.  This  includes 
straightening  the  road  by  eliminating  unnecessary  curves  and 
bends,  improving  the  grade  by  either  avoiding  or  cutting 
down  hills  and  embanking  valleys,  increasing  the  width 
where  requisite,  and  rendering  it  uniform  throughout  (Fig. 
13). 

2.  Drainage,  consisting  of  the  application  of  the  principles 
laid  down  for  the  drainage  of  new  roads,  and  in  the  construc- 
tion of  the  necessary  works. 

3.  Improvement  of  the  surface,  in  the  best  possible  manner. 

203 


204  THE  ART  OF  ROADMAKING 

Among  the  benefits  of  decreasing  length  and  reducing 
grades  are: 

1.  Saving  in  time. 

2.  Reduction  in  wear  and  tear  of  horses  and  equipment. 

3.  Saving  the  cost  of  maintenance  of  such  un- 
Benefits  of    necessary  portion. 

4"  Reduction  in  the  cost  of  haulage. 
5.  Saving  by  the   return  of  the   land   previously 
occupied  by  the  road  to  other  and  perhaps  more  renumerative 
uses. 

6.  Decrease  in  the  working  time  of  the  horses  and  a  slight 
increase  in  the  load. 

The  benefits  of  improving  the  surface  are  a  reduction  in  the 
cost  of  haulage  and  in  wear  and  tear  of  horses  and  vehicles. 

Clay  soils  can  be  improved  only  by  means  of  thorough 
drainage. 

If  sand,  gravel,  ashes,  coal-dust,  furnace-slag,  or  shells  can 
be  obtained,  a  coating  of  any  one  of  them,  4  inches  thick,  well 
compacted  by  rolling,  will  form  an  improvement; 
if  none  of  these  materials  can  be  obtained,  the  clay 
itself  may  be  utilized  by  being  burned,  as  described 
in  Chapter  VII. 

In  the  maintenance  of  clay  roads  sods  and  turf  should  not 
be  used  to  fill  holes  or  ruts,  as  they  soon  decay  and  form  soft 
mud;  neither  should  the  ruts  be  filled  with  field-stones,  as  they 
will  not  wear  uniformly  with  the  rest  of  the  road,  but  will 
produce  hard  ridges.  As  all  the  sun  and  wind  possible  are  re- 
quired to  keep  the  surface  in  a  dry  and  hard  condition,  trees 
and  close  hedges  should  not  be  allowed  within  200  feet  of  a 
clay  road. 

In  the  improvement  of  sand  roads  the  aim  is  to  make  the 
wheelway  as  narrow  and  well-defined  as  possible,  so  as  to 
have  all  the  vehicles  run  in  the  same  track.     An 
abundant    growth    of    vegetation    should    be    en- 
couraged on  each  side  of  the  wheelway,  to  prevent 
as  far  as  possible  the  shearing  of  the  sand.     Ditching  beyond 
a  slight  depth  to  carry  away  the  rain-water  is  not  desirable, 
for  it  tends  to  hasten  the  drying  of  the  sands,  which  is  to  be 


MAINTENANCE  OF  COUNTRY  ROADS  205 

avoided.  Where  possible  the  roads  should  be  overhung  with 
trees,  the  leaves  and  twigs  of  which  catching  on  the  wheelway 
will  serve  still  further  to  diminish  the  effect  of  the  wheels  in 
moving  the  sands  about.  If  clay  can  be  obtained,  a  coating 
6  inches  thick  will  be  found  a  most  effective  and  economical 
improvement.  A  coating  of  4  inches  of  loose  straw  will  in  a 
few  days'  travel  grind  into  the  sand  and  become  as  hard  and 
firm  as  a  dry  clay  road. 

MAINTENANCE  AND  REPAIRS 

Proper  maintenance  is  as  important  as  good  construction. 
This  consists  in  keeping  the  roadway,  as  nearly  as  practicable, 
in  the  same  condition  as  it  was  when  originally  made;  the 
repair  of  a  roadway  is  the  work  rendered  necessary  to  bring 
it  up  to  its  original  condition  after  it  has  become  deteriorated 
by  neglect  to  maintain  it.  There  is  a  wide  distinction  between 
the  two  operations;  the  former  keeps  the  road  always  in  good 
condition  while  the  latter  makes  it  so  only  occasionally. 

No  matter  how  well  a  road  may  be  made,  or  how  carefully 
the  materials  used  have  been  inspected,  it  will  soon  show  de- 
fects which  it  is  almost  impossible  to  guard  against, 

such  as  variableness  in  the  quality  of  the  material,    ec:e^slty  or 
......  maintenance. 

and  slighting  on  the  part  of  the  workmen.  More- 
over, every  material,  whether  natural  or  artificial,  is  con- 
tinually undergoing  a  process  of  deterioration  by  the  action  of 
the  elements.  The  materials  employed  for  pavements  are 
not  only  subjected  to  the  destroying  action  of  the  elements, 
but  also  to  abrasion  and  concussion,  which  by  themselves  are 
powerful  destroying  agents. 

The  essential  requisite  to  the  preservation  of  a  good  sur- 
face is  eternal  vigilance.  If  a  depression  appears  in  conse- 
quence of  settlement,  defective  material,  or  other  causes,  it 
must  be  at  once  eliminated;  if  not,  it  will  be  quickly  deepened 
and  enlarged  by  each  succeeding  vehicle,  and  will  thus  become 
an  obstacle  to  safe  traveling. 

Good  maintenance  comprises: 

1.  Constant  attention  to  repair  the  damages  made  by  traffic 
and  the  elements.  The  character  and  quantity  of  these  re- 


206 


THE  ART  OF  ROADMAKING 


(From  Good  Roads  Magazine,) 
FIG.  143. — Section  of  Country  Road  before  Improvement. 


(From  Good  Roads  Magazine.) 
FIG.  144. — Section  of  same  Road  after  Improvement. 


MAINTENANCE  OF  COUNTRY   ROADS  207 

pairs  will  vary  with  the  character  of  the  pavement  and  the 
manner  of  its  construction.  With  granite  blocks  laid  on  a 
concrete  foundation  they  will  be  the  least;  with  broken  stone 
they  will  be  the  greatest;  the  other  materials,  as  wood,  asphalt, 
and  brick,  lying  between. 

2.  Cleaning,   i.e.,   removing   the   detritus   caused   by   wear, 
horse-droppings,  and  other  refuse.     (See  Chapter  XIX). 


(From  Good  Roads  Magazine.) 

FIG.  145. — Section  of  same  Road  showing  effects    of   Travel,  resulting 
from  improper  Maintenance. 

3.  Laying  the  dust.     (See  Chapter  XL) 

The  most  obvious  feature  in  road  maintenance  is  the  ap- 
plication of  new  materials,  but  the  prevention  of  avoidable 
wear,  by  keeping  the  surface  and  the  body  of  the  road  in  good 
condition,  is  hardly  less  important;  and  the  removal  of  the 
materials  from  the  road  after  they  are  worn  to  detritus,  the 
care  of  the  surface,  and  attention  to  drainage,  are  essential 
parts  of  a  good  system  of  maintenance.  Experience  proves 
that  a  road  with  sufficient  strength,  good  surface,  and  thor- 
ough drainage  can  be  kept  in  first-rate  order  with  a  much 
smaller  quantity  of  materials  than  an  inferior,  ill-kept  road 


208  THE  ART  OF  ROADMAKING 

requires,  and  though  a  greater  amount  of  manual  labor  may 
be  necessary,  a  good  road,  on  the  whole,  is  generally  more 
cheaply  maintained  than  a  bad  one,  especially  when  there  is 
any  considerable  amount  of  traffic. 

There  are  three  principal  systems  of  maintaining  pavements: 

1.  By  contract,  at  a  fixed  price  per  square  yard  per  annum 

for  a  fixed  period.     This  method  is  used  for  asphalt 

Systems  of  pavements  m  both  the  United  States  and  Europe 
maintenance. r  .  . 

and  for  wood  pavements  in  ii/urope,  but  rarely  in 

America.  It  has  the  advantage  of  having  someone  admittedly 
responsible  for  the  condition  of  the  pavement,  but  it  is  the 
most  costly  system  and  there  is  always  difficulty  in  determin- 
ing the  exact  condition  of  the  pavement  at  the  expiration  of 
the  contract. 

2.  By  independent  contracts  for  the  labor  and  materials, 
the  tools  and  supervision  being  furnished  by  the  city. 

3.  By  men  in  the  employ  of  the  city.     This  is  the  most 
extensively  used  and  most  satisfactory  system. 

As  soon  as  a  country  highway  is  finished  and  opened  to 

traffic  a  system  of  maintenance  must  be  instituted.     No  style 

of  construction  is  sufficiently  permanent  to  admit 

Maintenance  of  tne  road  bemg  }eft  to  ta^e  care  of  itse}f       Whether 

roa^s"11  built  of  earth  or  stone,  it  will  eventually  wear 
into  ruts  and  holes,  the  time  depending  upon  the 
quality  of  the  material,  the  form  of  construction  and  the 
amount  of  traffic.  The  chief  object  in  the  maintenance  of 
an  earth  road  is  to  get  rid  of  the  water  as  quickly  and  as  fully 
as  possible.  In  maintenance,  as  in  construction,  water  is 
the  great  enemy  of  good  roads.  The  secret  of  success  in  main- 
tenance is  to  keep  the  surface  smooth  and  the  side  ditches 
open.  There  are  three  systems  in  vogue:  (1)  By  contract  with 
private  parties;  (2)  By  personal  service;  (3)  By  men  per- 
manently employed  for  the  purpose  by  the  community. 

1.  The    contract    system    is    unsatisfactory,   owing  to   the 
difficulty  of  getting  a  proper  observance  of  the  terms  of  the 
contract  from  the  contractor  or  his  employers. 

2.  The  personal-service  or  labor-tax  system  is  not  applicable 
to  the  maintenance  of  improved  roads,  nor,  in  fact,  to  any 


MAINTENANCE   OF  COUNTRY  ROADS  209 

class  of  roads;  it  is  unsound  in  principle,  unjust  on  its  opera- 
tion, wasteful  in  its  practice,  and  unsatisfactory  in  its  results. 

3.  The  system  of  permanently  employing  men  for  the  pur- 
pose by  the  community  has  been  adopted  by  France,  Germany, 
and  nearly  all  European  countries  and  by  the  New  York  State 
Highway  Commission,  and  has  many  advantages.  The  men 
so  employed  become  familiar  with  the  peculiarities  of  their 
sections  and  with  the  best  way  to  deal  with  them,  and  good 
men  soon  learn  to  take  an  interest  in  the  road  which  it  is 
their  business  to  keep  in  order. 

The  maintenance,  or  keeping  of  the  road  in  proper  order, 
consists  of: 

1.  Removal  or  prevention  of  the  detritus  either  in  the  form 
of  dust  or  mud,  and  removal  of  the  horse-droppings  and  other 
rubbish. 

2.  Filling  of  ruts  or  depressions. 

3.  Cleaning    out    of    the    ditches,    catch-basins,  and  water- 
courses. 

4.  Keeping  down  the  dust  in  dry  weather.     The  dust  pro- 
duced by  the  disintegrating  action  of  the  weather  and  the 
friction  of  the  traffic  renders  the  road  heavy  for  traffic  and 
annoys  passengers  and  horses. 

The  errors  commonly  committed  in  the  maintenance  of 
broken-stone  roads  are : 

1.  The  unskilled  application  of  materials. 

2.  Use  of  improper  and  unsuitable  materials. 

3.  Neglect  of  repairs. 

4.  Insufficient  and  unskillful  manual  labor. 
Well-made  roads  are  frequently  allowed  to  go  to  ruin  through 

these  wrongful  methods  of  maintenance,  requiring  at  some 
period  that  the  neglect  be  made  good  at  one  time,  instead  of 
the  work  being  spread  out  in  proper  maintenance  over  a  period 
of  years. 

The  cost  of  maintenance  varies  widely,  depending  princi- 
pally upon  the  degree  of  perfection  with  which  the  road  was 
originally  constructed,  and  is  largely  influenced  by 

the  class  of  labor  employed  in  maintenance. 

.  maintenance. 

The  factors  of  cost  of  maintenance  are: 

1.  The  quantity  of  material  that  will  be  required  to  replace 


210  THE  ART  OF   ROADMAKING 

the  annual  wear  caused  by  traffic  and  the  weather,  and  re- 
moved in  the  form  of  mud  and  dust,  depending  upon: 

a.  Width  of  road. 

b.  Nature   of   foundation,   drainage,   and   thickness   of 
crust. 

c.  Situation  of  the  road. 

d.  Quality  of  the  stone  to  be  applied. 

2.  Cost  of  the  material  procured  either  by  contract  or  by 
day  labor  under   the  supervision  of  the  authorities,  this   de- 
pending upon: 

a.  Cost  of  quarrying. 

b.  Cost  of  breaking. 

c.  Cost  of  hauling  from  quarry  to  roadside. 

d.  Cost  of  stacking  at  the  roadside. 

e.  Cost  of  loosening  the  stones  in  the  heaps.     A  con- 

siderable   item    in    frosty   weather   or   when   the 
stones  have  lain  for  some  time. 

f.  Cost  of  hauling  stones  from  depots  to  the  portion 

of  the  road  where  they  are  to  be  used. 

g.  Cost   of  preparing  the  4-oad-surface  to   receive   the 

stone, 
h.   Cost  of  spreading  the  stone. 

3.  Cost  of  compacting  the  stone. 

4.  Cost  of  cleaning  and  scraping. 

5.  Cost  of  cleaning  up  the   side   of  the  road,  ditches,  etc., 
and  keeping  open  watercourses,  depending  upon  the  frequency 
with  which  it  will  have  to  be  done,  usually  three  times  a  year 
is  sufficient. 

6.  Cost  of  dust  prevention. 

To  these  items  must  be  added  a  certain  sum  per  mile  for 
repair  and  replacing  of  tools,  etc.,  and  about  5  per  cent  on  the 
total  cost  to  cover  the  administrative  charges. 

Combining  these  factors  in  the  following  manner  will  give 
the  probable  cost  of  maintenance  per  mile  of  a  given  road.* 

*  Byrne,  "Highway  Construction,"  p.  668. 


MAINTENANCE   OF  COUNTRY  ROADS  211 

Let  N  =  average  number  of  cubic  yards  of  stone  spread  per 

mile; 

A  =  cost  per  cubic  yard  of  stone  in  depots; 
L=cost  of  preparing  road-surface  and  spreading  stone; 
R=  cost  per  cubic  yard  of  rolling; 

C=  average  number  of  times  sides  will  require  cleaning; 
c=cost  of  cleaning  sides,  etc.,  per  mile; 
S=  average  number  of  times  road  will  require  cleaning; 
s  =cost  of  cleaning  per  mile; 

W=  average  number  of  times  road  will  require  sprink- 
ling; 

w=cost  of  sprinkling  per  mile; 

D=  annual  depreciation  and  renewal  of  hand  tools; 
7=cost  of  administration,  say  5  per  cent  of  total  cost; 
X  =  cosi  of  maintenance  per  mile  per  annum. 
Then 

X=N(A+L+R)+Cc+Ss+Ww+D+l. 

If  stone  is  quarried  by  day's  labor,  its  cost  will  be 
A=q+b+h+p, 

in  which  q=cost  of  quarrying; 
6=  cost  of  breaking; 
h  =  cost  of  hauling; 
p=cost  of  stacking. 

Where  funds  have  been  provided  for  road  improvements, 
efforts  are  usually  directed  toward  building  as  much  road  as 
possible,  while  the  matter  of  maintenance  is  entirely  over- 
looked, and  no  funds  are  provided  for  needed  repairs.  The 
fact  that  no  great  inconvenience  or  damage  arises  from  a 
slight  depression  in  the  road  surface,  or  from  a  few  loose  stones, 
occasions  neglect,  and  the  condition  of  the  road  is  allowed 
to  become  gradually  worse.  When  the  surface  becomes,  in 
time,  so  rough  as  to  be  a  public  nuisance,  it  is  found  that  the 
cost  of  restoring  the  road  is  considerable;  moreover  the  rough- 
ness of  the  road  in  the  meantime  has  caused  a  "wear  and  tear", 


212  THE  ART  OF  ROADMAKING 

to  wagons,  carriages,  horses,  etc.,  which  is,  in  the  aggregate, 
of  considerable  importance. 

This  neglect  of  repairs  to  public  roads  is  very  poor  economy. 
It  would  be  a  remarkably  well-constructed  road  that  would 
not  show  some  defects  soon  after  it  began  to  be  extensively 
used.  With  the  greatest  possible  care  an  earth  roadbed  can- 
not be  made  strictly  uniform  as  to  solidity,  and  heavy  loads 
passing  over  the  crust  formed  by  the  stones  will  press  some  of 
the  stones  into  soft  places  in  the  earth  bed,  and  this  in  time 
will  cause  a  defect  on  the  surface  of  the  road.  A  very  slight 
depression  will  at  first  appear,  which  may  be  detected  only 
after  a  rain  (by  the  water  which  will  remain  for  some  time  in 
the  depression).  If  this  depression  is  permitted  to  remain 
it  will  soon  become  deeper  and  broader.  As  the  wagon  wheels 
go  in  and  out  of  it  they  grind  out  the  stone  softened  by  water, 
and  cut  down  the  sides,  so  that  what  was  at  first  a  slight  de- 
pression soon  becomes  a  hole.  Such  neglect  causes  subsequent 
repair  to  be  expensive. 

Some  of  the  causes  which  make  repairing  necessary,  and 
wkich  should  be  avoided  or  removed  as  far  as  possible  are: 

1.  Defective  construction  of  earth  bed. 
Causes 

which  make  2.  Failure  to  cut  off  under-ground  water  by 
repairs  drainage. 

3.  Rain  or  storm  water  permitted  to  lie  in 
pools  along  the  roadsides  or  in  side  ditches  which  do  not 
carry  the  water  from  the  road. 

4.  The  side  slope  being  insufficient  to  carry  the  storm  water 
from  the  road  to  the  side  ditches. 

5.  The  longitudinal  grade  of  the  road  being  greater  than  the 
slope  from  center  to  sides. 

6.  The  formation  of  ruts. 

7.  Raveling,  or  picking  up  loose  stone. 

8.  Surface  stone  not  of  proper  quality  and  not  uniform. 

9.  Roadbed  not  sufficiently  compacted. 

10.  Accumulation  of  trash  or  rubbish  on  the  road. 

When  the  road  reaches  the  condition  where  restoration  is 
necessary  the  work  should  be  done  in  sections  as  large  as 
convenient.  The  periods  at  which  the  restoring  or  recoat- 


MAINTENANCE  OF  COUNTRY  ROADS  213 

ing  of  a  broken-stone  road  will  be  required  depend  upon  the 
quantity  of  the  traffic,  and  vary  from  one  to  five  or 
more  years. 

The  methods  practiced  for  recoating  are:  (1)  the  surface  is 
cleaned  from  mud  and  dirt  and  the  new  stone  spread  over  it; 
sprinkled  and  rolled  in  the  same  manner  as  a  new  construc- 
tion; (2)  the  surface  is  "  scarified,"  or  loosened  or  broken  up 
by  picking  or  ploughing,  before  spreading  the  new  stones. 
The  object  of  this  is  to  enable  the  new  stones  to  become  more 
completely  incorporated  with  the  old  material. 

For  the  proper  care  of  the  roadway,  an  adequate  number 
of  skilled  laborers  are  necessary.  This  labor  should  be  per- 
manently employed  by  the  community,  and  should  be  under 
the  direct  orders  and  supervision  of  the  engineer  in  charge  of 
the  road.  The  force  should  consist  of  the  engineer  in  charge, 
assistant  engineers  or  inspectors,  chief  foreman,  foremen  and 
laborers. 

The  following  instructions  to  Roadmen*  will  be  found 
useful : 

"  1.  Never  allow  a  hollow,  a  rut,  or  a  puddle  to 

remain  on  a  road,  but  fill  it  up  at  once  with  chips  ,] 

..  to  roadmen. 

from  the  stone-heap. 

2.  Always  use  chips  for  patching,  and  for  all  repairs  during 
the  summer  months. 

3.  Never  put  fresh  stones  on  the  road  if  by  cross-picking  and 
a  thorough  use  of  the  rake  the  surface  can  be  made  smooth  and 
kept  at  the  proper  strength  and  section. 

4.  Remember  that  the  rake  is  the  most  useful  tool  in  your 
collection,  and  that  it  should  be  kept  close  at  hand  the  whole 
year  round. 

5.  Do  not  spread  large  patches  of  stone  over  the  whole  width 
of  the  road,  but  coat  the  middle  or  horse  track  first,  and  when 
this  has  worn  in,  coat  each  of  the  sides  in  turn. 

6.  Always  arrange  that  the  bulk  of  the  stones  may  be  laid 
down  before  Christmas. 

7.  In  moderately  dry  weather  and  on  hard  roads,  always  pick 
up  the  old  surface  into  ridges  six  inches  apart,  and  remove 
all  large  and  projecting  stones  before  applying  a  new  coating. 

*  Road  Improvement  Association,  London,  England. 


214  THE   ART   OF  ROADMAKING 

S.  Never  spread  stones  more  than  one  stone  deep,  but  add  a 
second  layer  when  the  first  has  worn  in,  if  one  coat  be  not 
enough. 

9.  Use  a  steel-pronged  fork  to  load  the  barrels  at  the  stone- 
heap,  so  that  the  siftings  may  be  available  for  " binding" 
and  for  summer  repairs. 

10.  Never  shoot  stones  on  the  road,  and  crack  them  where 
they  lie,  or  a  smooth  surface  will  be  out  of  question. 

11.  Go  over  the  whole  of  the  new  coating  every  day  or  two 
with  the  rake,  and  never  leave  the  stones  in  ridges. 

12.  Remove   all  large   stones,   blocks   of   wood,    and   other 
obstructions   (used  for  diverting  the  .  traffic)   at  nightfall,   or 
the  consequences  may  be  serious. 

13.  Never  put  a  stone  upon  the  road  for  repairing  purposes 
that  will  not  pass  freely  in  every  direction  through  a  2-inch 
ring,  and  remember  that  still  smaller  stones  should  be  used 
for  patching  and  for  all  slight  repairs. 

14.  Recollect  that  hard  stone  should  be  broken  to  a  finer 
gauge  than  soft,  but  that  the  2-inch  gauge  is  the  largest  that 
should  be  employed  under  any  circumstances  where  no  steam 
roller  is  employed. 

15.  Never  be   without  your  ring-gauge.     It   should   be   to 
the  roadman  what  the  compass  is  to  the  mariner. 

16.  If  you  have  no  ring-gauge,  remember  Macadam's  advice 
that  any  stone  you  cannot  put  easily  into  your  mouth  should 
be  broken  smaller. 

17.  Use  chips,  if  possible,  for  binding  newly  laid  stones  to- 
gether, and  remember  that  road-sweepings,  horse-droppings, 
sods  of  grass,  and  other  rubbish,  when  used  for  this  purpose, 
will  ruin  the  best  road  ever  constructed. 

18.  Remember  that  water-worn  or  rounded  stones  should 
never  be  used  upon  steep  gradients,  or  they  will  fail  to  bind 
together. 

19.  Never  allow  dust  or  mud  to  lie  on  the  surface  of  the  road, 
for  either  of  these  will  double  the  cost  of  maintenance. 

20.  Recollect   that  dust   becomes  mud  at  the  first  shower, 
and  that  mud  forms  a  wet  blanket  which  will  keep  a  road  in  a 
filthy  condition  for  weeks  at  a  time,  instead  of  allowing  it  to 
dry  in  a  few  hours. 

21.  See  that  all  sweepings  and  scrapings  are  put  into  heaps 
and  carted  away  immediately. 

22.  Remember  that  the  middle  of  the  road  should  always  be  a 


MAINTENANCE   OF  COUNTRY  ROADS  215 

little  higher  than  the  sides,  so  that  the  rain  may  run  into  the 
side  gutters  at  once. 

23.  Never  allow  the  water-tables,  gutters,  and  ditches,  to 
clog  up,  but  keep  them  clear  the  whole  year  through. 

24.  Always  be  upon  your  road  in  wet  weather,  and  at  once 
fill  up  with  "  chips  "  any  hollows  or  ruts  where  the  rain  may  lie. 

25.  When  the  main  coatings  of  stone  have  worn  in,  go  over 
the  whole  road,  and,  gathering  together  all  the  loose  stones, 
return  them  to  the  stone-heap  for  use  in  the  winter  to  follow; 
for  loose  stones  are  a  source  of  danger  and  annoyance  and  should 
never  be  allowed  to  lie  on  any  road." 

.     The  proper  season  for  laying  the  bulk  of  the  fresh  materials 
j  is  in  the  autumn  and  early  winter.     The  precise  time  at  which 
:it  can  be  begun  will  depend  on  the  climate,  weather, 
•subsoil  and  the  nature  of  the  material.     As  soon  as 
'the  surface  of  the  road  softens  from  the  wet,  patch- 
ing  of   hollows,  or  wheel  tracks,  and  channels  worn  by  water, 
should  be  commenced,  the  mud  having  been  previously  re- 
1  moved  where  necessary.     The  greater  part  of  the  new  materials 
should  be  put  on  before  the  end  of  the  year,  so  that  they  may 
be  at  least  partially  worked  in  before  winter,  when  they  are 
most   required   in  the   road,   and  before  severe  frost   comes. 
Unconsolidated  materials  are  more  annoying  to  the  traffic  in 
frosty  weather,  and  there  is  waste  by  the  stones  being  crushed 
and  scattered  instead  of  being  incorporated  in  the  road.     Stones 
laid  late  in  the  winter  seldom  consolidate  thoroughly,  and  those 
laid  in  the  spring  hardly  set  at  all,  but  work  loose  in  the  dry 
weather,  if  they  are  not  of  a  binding  nature.     If  a  road  from 
any  cause  shows  weakness  in  the  spring,  and  requires  stoning, 
everything  must  be  done  to  aid  consolidation,  and  great  atten- 
tion to  the  newly  laid  materials  will  be  required.     All  stones 
which  do  not  bind  must  be  raked  off  as  the  season  advances 
and  there  is  no  longer  any  prospect  of  their  working  in. 

The  autumn  work  on  roads  is  generally  commenced  after 
harvest,  as  the  additional  men  which  are  required  are  then 
more  easily  to  be  had.  Cleaning  up  the  sides  cannot  be  well 
done  in  dry  weather,  but  the  constant  laborers  should  take 
advantage  of  suitable  moist  weather  to  get  forward  with  it, 
so  that  the  water-tables  may  be  cleared,  the  outlets  to  the  side- 


THE 

UNIVERSITY 


216 


THE    ART    OF   ROADMAKING 


ditches  opened,  and  the  sod  bordering  trimmed  before  the  wet 
weather  sets  in.  If  the  manual  labor  be  allowed  to  get  behind- 
hand in  the  autumn,  there  is  often  little  chance  of  roads  re- 
covering it  until  the  winter  is  over.  Scraping  is  very  necessary 
as  soon  as  rainy  weather  commences,  to  get  rid  of  the  mud 
which  then  forms  on  the  surface  from  the  effects  of  the  wear 
in  the  summer.  As  soon  as  the  cleaning  up  of  the  sides  is 
finished,  and  the  scraping  is  well  forward,  the  laying  of  materials 


FIG.  146.— A  Well-kept  Country  Road. 

in  small  patches  should  begin.  The  first  patches  should  be 
laid  in  places  naturally  damp,  and  when  the  road  generally 
begins  to  soften  from  the  wet  weather,  spreading  materials 
and  scraping  will  take  up  all  the  constant  laborers'  time,  and 
usually  requires  casual  labor  besides  until  the  middle  of  De- 
cember, or  even  later.  In  the  beginning  of  the  year,  after  the 
great  bulk  of  materials  has  been  spread,  less  labor  is  necessary; 
only  small  patches  to  make  good  weak  places  which  have 
shown  themselves  during  the  winter  remain  to  be  laid,  and 
scraping  is  hindered  by  frost,  and  by  the  consolidated  materials 


MAINTENANCE  OF  COUNTRY   ROADS  217 

about  the  road.  As  the  spring  advances  more  scraping  will 
be  required  in  damp  weather,  and  in  dry  weather  the  stones 
which  have  not  worked  in  will  require  the  roadman's  attention, 
and  must  be  raked  off  if  they  will  not  set.  The  spring  and 
early  summer  is  the  best  season  for  cleaning  out  side-ditches 
which  are  not  too  wet.  The  stuff  is  moved  easier  when  still 
moist,  and  it  is  well  to  get  forward  with  work  of  this  sort  in 
the  spring,  and  not  to  leave  it  till  the  autumn,  when  there  is 
so  much  other  work  to  be  done. 


CHAPTER  XI 
THE  CONTROL  AND   PREVENTION   OF   ROAD  DUST  * 

ON  wood,  asphalt,  stone,  and  brick  pavements,  the  wear  is 
so  slow  as  to  be  practically  negligible,  and  dust  arising  from  any 
of  these  surfaces  is  produced  by  extraneous  matter  brought 
to  the  road  in  various  ways  from  outside  sources.  But  in  the 
case  of  macadamized  roads  one  of  the  most  important  problems 
that  has  yet  been  forced  to  the  attention  of  road  engineers  and 
municipal  officials  is  the  suppression  or  prevention  of  dust 
arising  from  the  road  itself.  There  is  hardly  a  section  of  the 
country  in  which  this  problem  has  not  had  the  consideration  of 
local  officials,  and  the  lack  of  information  as  to  how 
Importance  ^o  overcome  it  has  resulted  in  many  cases  of  trans- 
prevention.  f°rmmg  the  "dust  nuisance"  into  a  mud  or  slime 
nuisance.  This  is  especially  so  in  rural  districts 
where  many  officials  have  purchased  oil  without  proper 
knowledge  of  its  ingredients  and  its  adaptability  for  use 
on  the  roadways  of  their  districts,  and  have  spread  the 
oil  broadcast  over  the  highways,  transforming  them  into 
slippery  mires  and  making  them  unsafe  for  traffic  of  any  kind. 

The  "dust  nuisance"  is  not,  however,  so  much  the  result 
of  the  natural  formation  of  dust  by  ordinary  and  reasonable 
traffic,  as  it  is  of  the  use  of  automobiles,  the  wheels  of  which 
draw  out  and  throw  into  the  air  the  particles  that  would  other- 
wise fill  the  crevices  and  act  as  a  bond  between  the  broken 
stones  of  the  macadam  construction. f 

Dust  has  always  been  a  feature  of  broken-stone  roajds,  being 
at  the  same  time  the  result  of  use  and  a  check  upon  excessive 

*  The  best  general  treatise  on  this  subject  is  "Road  Preservation  and 
Dust  Prevention,"  by  William  Pierson  Judson,  from  which  much  of  the 
data  of  this  chapter  has  been  drawn. 

t  See  Appendix  III,  "Concerning  the  Wear  of  Roads  by  Automobiles." 

218 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST     219 

wear.  Whenever  the  surface  becomes  free  from  dust,  by  wind 
effect  or  otherwise,  it  has  been  necessary  to  spread  a  thin  layer 
of  sand  or  screenings,  or  other  fine  material,  as  a 
protection  to  the  stone  fragments  forming  the  road,  Value  and 
and  to  prevent  them  from  "raveling"  or  losing  road  dust. 
their  bond.  When  these  stones  or  the  screenings 
forming  the  protective  layer,  or  both,  consist  of  limestone, 
the  resulting  impalpable  dust  is  most  objectionable  to  people 
driving  upon  the  road  and  even  more  so  to  those  living  along 
it.  When  this  limestone  dust  is  wet,  the  resulting  mud  is 
the  most  slippery  and  dangerous  for  rubber-tired  wheels, 
causing  more  side-slip  than  any  other  material  used  for 
roads. 

In  1905,  when  automobiles  became  common,  the  raising  and 
scattering  of  road-dust  increased  greatly,  and  in  the  summer 
of  1906,  when  their  use  greatly  increased  both  in  Europe 
and  in  the  United  States,  the  subject  at  once  became  acute, 
and  road-builders  everywhere  found  that  a  new  condition  had 
suddenly  developed,  particularly  on  those  mac- 

adam roads  radiating  from  the  cities  where  auto-    Effects  of 

!  -i  i       rm  f         i     ji          ±1        automobile 

mobiles    were    most    used.     They   found   that   the 


preservation  of  the  roads  demanded  a  better  and 
more  enduring  surface,  and  one  that  will  neither  require  nor 
produce  the  loose  surface  layer  which  had  heretofore  been  a 
necessary  feature. 

In  the  Minutes  of  Proceedings  of  the  Institution  of  Civil 
Engineers  (London)  for  September,  1906,  it  is  said: 

"Experience  has  proved  that  the  broad  pneumatic  tires  of 
heavy  motor-cars  at  high  speed  draw  out  the  small  particles 
which  bind  the  material  of  a  macadamized  road.  On  the  main 
roads*  more  than  half  the  traffic  is  of  motor-cars,  which  may 
reasonably  be  expected  to  become  a  more  and  more  popular 
means  of  travel,  to  which  the  roads  must  now  be  adapted  by 
introducing  into  them  some  material  which  would  make  them 
dustless;  for  which  purpose,  tar,  or  some  tar  derivative,  is 
the  only  remedy  now  in  sight.  Motors  have  come  to  stay, 

*  Of  England. 


Before  Treatment. 


(Courtesy  of  Standard  Oil  Company.) 
After  Treatment. 
FIG.  147.— The  Dust  Nuisance  and  Its  Abolition.         220 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST  221 

and  the  road-builders  mean  to  make  the  roads  fit  to  carry 
them." 

That  this  condition  equally  concerns  the  road-builders  of 
the  United  States  is  shown  in  the  1907  report  of  Logan  W.  Page, 
Director  of  the  U.  S.  Office  of  Public  Roads,  in  which  he 
says : 

"In  recent  years  perhaps  the  most  important  and  certainly 
the  most  difficult  problem  which  has  engaged  the  attention  of 
highway  engineers  is  the  prevention  of  dust.  Until  the  general 
introduction  of  motor  vehicles,  dust  was  considered  as  neither 
more  nor  less  than  a  nuisance.  The  problem  has  now,  how- 
ever, assumed  a  more  serious  aspect.  The  existence  of  our 
macadam  roads  depends  upon  the  retention  of  the  road-dust 
formed  by  the  wearing  of  the  surface.  But  the  action  of 
rubber-tired  motor-cars  moving  at  high  speed  soon  strips  the 
macadam  road  of  all  fine  material,  the  result  being  that  the 
road  soon  disintegrates.  .  .  .  This  is  a  subject  which  should 
engage  the  earnest  attention  of  the  National  Government  at 
once.  No  matter  how  important  we  may  deem  the  building 
of  good  roads,  we  cannot  but  consider  it  even  more  important 
to  preserve  those  which  have  already  been  constructed." 

James  Owen,  M.  Am.  Soc.  C.E.,  one  of  the  most  experienced 
of  American  road  engineers,  in  a  paper  on  "Highway  Con- 
struction," before  the  1906  meeting  of  the  American  Society 
of  Municipal  Improvements,  said: 

"Every  system  of  road  construction  should  be  immediately 
supplemented  by  a  maintenance  organization,  as  in  time  the 
construction  department  disappears,  but  the  maintenance  de- 
partment is  permanent,  and  is  the  vital  point  in  the  future 
road-development  of  the  country.  .  .  .  The  automobile 
is  demanding  attention  from  engineers  as  to  whether  there 
should  not  be  new  means  and  methods  for  road  mainten- 
ance." 

Similar  statements  of  motor-car  effects,  made  by  govern- 
ment commissioners,  civil  authorities,  engineers,  and  in  period- 
icals, all  tend  to  show  the  dangers  of  road  dust  and  the  im- 
portance of  its  prevention. 

The    demand    for   relief   comes    not   only  from  recognized 


222 


THE  ART  OF  ROADMAKING 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST      223 

authorities  and  from  the  road  users,  but  also  from  the  property 
owners    who    live    along   the    roads,    and    pay    for 
them,  and  who  find  that  the  former  dust  to  which   Necessity 
they    had    objected   has   become    an   hundred-fold    preventjon 
worse    and    not    to    be    endured;     some    country 
residences  which  have  long  been  desirable  and  valuable,  have 
suddenly  become  neither  tenantable  nor  salable,  and  others 
have  been  sold  for  half  their  cost  because  of  the  dust  from 
adjacent  roads.     In   Massachusetts   passing  motor-cars  have 
even  thrown  up  fragments  of  road-stones  into  the  windows  of 
houses. 

The  situation  is  well  stated  in  the  following  quotation  from 
the  1907  report  of  the  Massachusetts  Highway  Commission, 
which  has  built  and  maintains  the  main  parts  of  one  of  the 
finest  road  systems  in  the  United  States: 

"Perhaps  the  most  important  discovery  of  the  year  is  the 
extraordinarily  destructive  effects  upon  stone  roads  of  the  large 
number  of  swiftly  moving  automobiles.  Practically  all  the 
main  roads  are  thus  affected.  It  has  been  noted  that  the  binder 
is  swept  from  the  road,  and  that  the  number-two  stone  (?-in. 
to  IJ-in.  size)  is  disturbed;  in  some  instances  standing  on  the 
surface,  and  in  others  being  left  in  windrows  along  the  road- 
side. The  Commission  is  satisfied  that  a  material  change  in 
the  methods  of  maintaining  stone  roads  must  be  made.  While 
old  methods  have  proved  satisfactory  in  the  past,  they  fail 
under  the  present  usage.  The  automobile  has  come  to  stay 
and  will  increase  in  numbers,  and  it  must  be  reckoned  with." 

The  1908  report  of  the  Commission  says: 

"The  destructive  work  of  automobiles  during  the  past  year 
was  even  more  marked  than  it  was  in  1906." 

These  conditions  and  the  opinions  cf  various  authorities, 
have  led  to  a  great  amount  of  experimental  work,  and  to  the 
invention  of  many  processes  and  devices  having  for  their  object 
either  temporary  treatments  which  should  hold  the  dust  in 
place,  or  better,  the  adoption  of  more  permanent  methods 
which  will  prevent  the  formation  of  dust,  and  which  will  be 
applicable  to  the  many  thousands  of  miles  of  existing  fine  roads 
of  broken-stone  which  Europe  has  had  for  nearly  a  century  and 


224 


THE  ART  OF   ROADMAKING 


(Courtesy  of  the  Barrett  Mfg.  Co.) 

FIG.    149. — Western,   Mass.     On   Boston-New  York   Automobile   Route. 
A  turn  protected  for  two  years  with  tarvia. 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST  225 

parts  of  America  for  one-tenth  as  long,  and  which  must  now 
be  saved  from  threatened  destruction. 

The  English  engineers  have  had  the  advantage  of  an  abun- 
dant and  cheap  supply  of  coal-tar,  and  have  taken  the  lead  in 
efforts  to  find  ways  to  get  the  best  results  from  applying  it 
— as   well   as   various   oil-emulsions — to   parts   of  their  great 
extent  of  fine  and  old  roads.     The   French  engi- 
neers, whose  national  road   system  in  its  general  General 
scheme    and    organization    and    in    the    details    of  experiments. 
its    execution    and    maintenance,    is   the    finest   in 
the  world,  have  devised  and  widely  used  methods  for  apply- 
ing bituminous  binders  and  coatings  to  road  surfaces,  while 
American  engineers  have  produced  the  best  form  of  bituminous 
macadam,  or  bitulithic,  as  well  as  the  appliances  for  making 
it  of  uniform  reliability  and  upon  a  large  scale. 

Americans  have  also  invented  a  method  for  the  consolidation 
and  asphaltic  treatment  of  sandy  and  other  soils,  using  a 
peculiar  "rolling  tamper"  and  heavy  asphaltic  oil,  and  have 
made  in  California  many  hundreds  of  miles  of  dustless  roads 
which  are  comparatively  cheap  and  which  there,  in  the  absence 
of  heavy  rains  and  deep  frosts,  are  durable. 

The  dust  problem  is  open  to  two  methods  of  attack:  (1)  by 
applying  materials  to  the  road  which  will  hold  down  the  dust 
formed,  or  (2)  by  methods  of  construction  designed 

to  reduce  the  formation  of  dust,  and  therefore  the  Methods 
c  .1  •,  .    .  of  dust 

wear  of  the  road,  to  a  minimum.  prevention. 

The  following  are  the  general  methods  in  use  for 
preventing   or    reducing    dust.     Each    method    more    or   less 
retains  or  agglomerates  the  dust  already  formed  or  prevents  its 
formation;  the  first  form  being  classed  as  temporary  binders 
and  the  last  two  as  permanent  binders. 

1.  Sprinkling  roads  with  fresh  water. 

2.  Sprinkling  roads  with  natural  salt  water. 

3.  Sprinkling   roads   with   mixture   of   water   and    calcium 
chloride. 

4.  Sprinkling  roads  with  an  oil  emulsion. 

5.  Impregnating  roads  with  special  crude  oils. 

6.  Impregnating  road  surfaces  with  special  coal-tar  products. 


FIG.  150. — Studebaker  Road  Oiler. 


FIG.  151. — The  "Topping"  Oiler  in  Operation.  226 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST     227 

The  most  common  and  the  most  costly  way  to  prevent  dust 
and  to  preserve  roads  is  to  sprinkle  them  with  water.  To 
keep  roads  always  wet  entails  expense  which  is 
prohibitive  even  for  city  streets  and  park  roadways, 
on  some  of  which  $700  to  $900  per  mile  per  year  is  expended 
for  sprinkling  thirty  to  forty  feet  width,  in  order  to  make  them 
dustless  during  an  average  of  six  hours  per  day.  During  dry 
and  hot  weather  the  sprinkling  to  be  effective  must  be  repeated 
several  times  per  day  and  the  surface  alternates  between  mud 
and  dust.  When  tried  on  rural  roads  it  has  usually  been  in- 
effective, costly,  and  soon  abandoned. 

Sea-water  is  used  with  results  even  more  unsatisfactory,  for 
although  the  hygroscopic  effect  of  the  deposited  salt  prolongs 
the  duration  of  moisture  on  the  road,  its  presence 
in  the  dust  and  mud  adds  to  their  injurious  effects; 
the  salty,  sticky  mud  damaging  vehicles,   corroding   metals, 
and  loosening  the  fragments  of  stone.     Moreover,  the  accumu- 
lated salt,  when  dry,  hurts  throats  and  eyes,  damages  cloth- 
ing, furniture  and  to  some  extent  the  feet  of  horses. 

Calcium  chloride  in  solution  has  been  used  as  a  substitue  for 
water,  giving  a  slightly  better  effect  at  about  the  same  cost. 
The  principle  of  this  method  is  that  this  salt  is 
hygroscopic  and  when  mixed  into  the  road  surface 
(by  means  of  having  it  in  solution  in  the  water 
of  the  sprinkling  cart)  it  absorbs  additional  moisture  from  the 
air,  thus  rendering  continuous  moisture  without  the  frequent 
sprinkling  necessary  with  water.  It  also  has  a  feeble  chem- 
ical action  which  unites  some  of  the  silicates  of  the  macadam. 
While  the  limited  experiments  in  this  country  have  met  with 
some  success,  its  principal  use  is  in  England,  where  the  moist 
climate  offers  favorable  conditions  and  where  over  two  hundred 
of  the  local  road  authorities  are  using  it  increasingly.  Its  weak 
solution  is  non-corrosive  and  harmless. 

The  process  is  best  suited  to  special,  limited  cases  of  fine 
residence  streets  adjoining  large  cities,  where  a  municipal 
supply  of  hydrant-water  is  available  for  sprinkling,  and  it  is 
specially  applicable  as  preparation  for  parades  or  road  races. 
At  the  best,  the  effects  of  calcium  chloride  are  temporary  and 


228 


THE  ART  OF  ROADMAKING 


make  no  radical  betterment  in  the  road  surface.  It  is  not 
applicable  to  the  great  extent  of  existing  broken-stone  roads 
which  have  no  water  supply,  and  which  demand  permanent 
treatment  to  check  wear  in  order  to  reduce  dust,  which  is  more 
or  less  true  also  of  all  patented  solutions. 

Oil  emulsions  are  practically  mixtures  of  water,  oil  and  alkali 
(as  ammonia  or  potash) ;  they  are  more  easily  and  cheaply 
applied  than  oils  and  they  avoid  some  of  the  obvious 


(Courtesy  of  Standard  Oil  Company) 
FIG.  152. — Sprinkling  Road  Oil  Emulsion  from  Ordinary  Watering  Can. 

objections  to  the  use  of  oils.  Their  effects  on  road-dust  are 
Oil  Emul-  usually  only  temporary,  but  the  results  are  im- 
sions.  mediate  and  travel  is  not  interrupted. 

There  are  in  use  many  processes,  patented  and  otherwise, 
for  making  and  applying  emulsions  of  oil,  including  vegetable 
oils,  crude  petroleum,  residual  oil,  creosote-oil,  oil-tar,  coal-tar, 
and  similar  materials,  in  all  of  which  cases  some  way  is  found 
to  emulsify  the  oily  or  bituminous  material  in  water,  so  that 
the  mixture  can  be  spread  by  a  sprinkling  or  a  spraying  device, 
or  usually  by  an  ordinary  watering-cart.  The  results  are  more 
lasting  than  those  from  the  chemical  salts  mentioned  above. 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST     229 

Many  unsuccessful  attempts  have  been  made  to  use  Pennsyl- 
vania and  Ohio  oils  having  a  paraffin  base,  or  some  of  the  Rus- 
sian oils  having  a  naphtha  base,  both  in  their  crude  form  and 
in  emulsions;  but  these  have  all  failed,  because  such  petro- 
leums are  not  suited  to  roadwork,  refusing  to  bind  the  road 
materials,  having  an  ill  order  and  forming  a  greasy  slime. 

Oils  having  an  asphaltum  base,  like  some  of  the  petroleums 
of  California,  Texas,  Oklahoma,  Kansas,  and  Kentucky  in  the 
United  States,  and  some  from  Galicia  and  from  Baku  in  Europe, 
are  the  only  ones  suitable;  but  if  any  kind  of  oil  is  sprayed  or 
sprinkled  in  its  crude  form  on  a  hard  macadam  road,  the  re- 
sult is  liable  to  be  most  objectionable  in  regions  of  normal  rain- 
fall, which  may  mix  the  oil  into  injurious  mud. 

All  oil  mixtures  in  which  acids  or  alkalies  are  used  to  form 
soapy  emulsions  which  will  mix  with  water,  may  be  expected 
to  cause  the  subsequent  road-dust,  even  though  it  be  slight  in 
quantity,  to  be  irritating  and  injurious  to  the  throat,  eyes  and 
skin,  in  proportion  to  the  acridity  of  the  solvent,  and  some  of 
the  mixtures  have  been  disused  for  that  reason. 

Attempts  have  been  made  since  1894  to  use  crude  petroleum 
or  some  of  its  derivatives,  or  some  oily  by-product  of  gas  manu- 
facture, to  control  and  prevent  dust.  These  at- 
tempts,  many  of  them  unsuccessful,  have  led  to 
knowledge  as  to  the  kinds  of  oil  which  are  unsuitable  and  as  to 
the  conditions  which  cause  failure.  Experience  has  also  shown 
that  oils  of  certain  characteristics,  properly  applied  under  the 
right  conditions,  give  good  results  at  reasonable  costs.  There 
will  undoubtedly  be  a  great  increase  in  the  near  future  in  the 
use  of  heated  asphaltic  oils,  not  only  to  prevent  dust,  but  also 
to  improve  sandy  roads  and  to  preserve  gravel  and  broken- 
stone  roads. 

Crude  petroleums,  which  contain  the  largest  proportion  of 
pure  asphaltum,  give  the  best  results.  Petroleum,  without 
asphaltum,  having  a  paraffin  base,  and  those  having  a  naphtha 
base,  are  useless,  as  mentioned  above.  Some  of  the  Cali- 
fornia oils  as  they  come  from  the  wells,  especially  those  in 
the  Bakersfield  district,  producing  petroleums  having  60  to 
84  per  cent  of  pure  asphaltum,  are  valuable  mainly  for  their 


230  THE  ART  OF  ROADMAKING 

use  on  roads  and  are  used  in  a  crude  state  with  most  satis- 
factory results.  Petroleums  with  asphaltic  bases  from  Texas, 
Kentucky,  Kansas  and  Oklahoma,  some  of  the  Russian  oils 
from  Baku,  and  those  from  Galicia  (Austria)  and  Borneo 
are  valuable  mainly  for  their  volatile  parts,  leaving  residuum 
which  is  effective  for  roadwork  after  distillation  has  removed 
the  naphtha,  gasoline,  illuminating-oil,  and  other  elements 
which  would  be  detrimental  to  roads.  The  by-products 
thus  left  are  variously  known  as  "  residual  oil/'  "  roadbed 
oil,"  "steamer-oil,"  and  other  trade  names. 

California  crude  petroleum,  heavy  in  asphaltum,  which  is 
98  per  cent  pure,  was  first  used  for  roadwork  at  Santa  Barbara 
in  1894  and  its  use  in  its  native  state  has  since  been  general  and 
in  most  cases  successful;  but  its  general  use  throughout  the 
country  is  prevented  by  difficulties  of  transportation. 

It  has  been  a  common  thing  during  the  past  few  years  for 
some  county  official,  to  whom  all  oils  look  alike,  to  buy  a 
car-load  of  oil  of  unknown  quality  and  to  have  it  sprinkled 
from  watering-carts  in  unrestricted  quantity,  without  experi- 
enced direction  or  regard  to  details  of  road  con- 
Inexperience  dition  or  of  weather,  and  without  attempt  to 
m  handling  * 

road  oils.       remove   or   to   cover   the   greasy   mud    caused    by 

sudden  rainfall,  or  to  warn  the  traffic  to  avoid 
the  fresh  oil.  It  gets  on  everything — on  plants,  bushes, 
trees,  vehicles,  and  clothes,  and  the  results  have  often  been 
most  objectionable  to  residents  and  have  caused  opposition 
and  waste  which  good  management  would  have  avoided. 

It  has  been  demonstrated,  however,  that  the  objectionable 
features  are  avoidable  by  the  successful  use  of  crude  and 
residual  oils  in  various  parts  of  this  and  other  countries. 
It  has  also  been  shown  that  the  oil  sprinkled  over  the  surface 
of  a  macadam  road  does  not  save  the  road  from  wear  but 
merely  stops  the  dust;  and  that  a  light  coating  of  sand 
shaken  over  the  freshly-oiled  surface  will  stop  spattering  of 
the  oil,  which  was  the  cause  of  many  of  the  complaints. 

The  types  of  oiled  roads  peculiar  to  California  have  been 
evolved  from  the  local  conditions  of  material  and  climate,  and 
the  results  have  been  such  as  to  induce  efforts  to  adapt  the  best 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST    231 

of  these   constructions   to   other   conditions   elsewhere.     This 
consists  in  mixing  heated  asphalt ic  oil  with  loosened,  mois- 
tened soil,  and  consolidating  with  a  "  rolling  tamper  "  into 
a  firm,  smooth,  six-inch  layer,  which  is  durable  and  dustless. 
In  the  best  practice  the  crown  of  a  road  of  soft  materials 
to  be  oiled  must  be  high  and  its  sides  well  drained, 
because    water    with    or    without    freezing    floats  General 
much  of  the  oil  or  gets  under  the  oiled  crust  and  oiling  roads 
softens  it.     The  hotter  the  oil  when  applied,  the 
warmer  the  weather  and  dryer  the  road,  the  better. 

In  California,  according  to  soil,  from  175  to  400  and  some- 
times 600  barrels  (of  42  gallons  each)  of  asphaltic  oil  are 
needed  per  mile  of  10-  to  16-foot  road  per  year.  Two  or 
three  treatments  are  needed  on  a  new  road  during  the  first 
year  if  the  road  is  of  a  loamy  or  sandy  nature.  After  a  road 
has  been  well  oiled  and  a  crust  is  formed,  care  must  be  taken 
not  to  break  through  the  crust.  Prompt  repairs  are  impera- 
tive. It  is  better  to  use  several  successive  applications  than 
to  flood  the  road  with  oil. 

Road  materials,  which  if  wet  would  pack  firmly  under 
roller  or  traffic  and  still  remain  slightly  porous,  are  the 
materials  which  are  the  best  for  use  by  saturating  with 
suitable  thick  adhesive  oils.  Such  oils  suppress  dust  and 
harden  the  road.  Road  materials  of  certain  clays,  earths, 
gravels,  which  when  wet  pack  tight  or  bake  in  the  sun  and 
which  pulverize  into  dust,  must  be  either  loosened  by  harrow- 
ing, or  otherwise  made  porous  before  being  oiled,  and  then 
must  be  covered  with  sand,  screenings  or  the  material  of 
the  road.  Oiling  roads  is  a  case  where  a  little  knowledge 
is  dangerous,  and  where  much  knowledge  and  experience  must 
be  employed  to  select  suitable  oils  and  to  use  them  correctly. 

Refined  coal-tar,  produced  in  gas  manufacture  and  treated 
to  remove  its  injurious  parts  and  yet  to  preserve  its  ductility 
and  to  secure  uniformity,  has  been  generally  ac- 
cepted by  the  road  authorities  of  France  and  Eng-        Coal-tar 
land,  and  also  by  those  road-engineers  in  the  United        tions!™ 
States  who  have  given  the  subject  most  attention, 
as  being  the  best   material    with   which   to  improve  broken- 


232 


THE  ART  OF  ROADMAKING 


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THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST     233 

stone  roads ;  binding  the  surface  of  existing  roads  and  bettering 
the  construction  of  new  roads,  thereby  preventing  the  forma- 
tion of  road  dust.  Experience  in  1910  favors  use  of  asphaltic 
residual  oils  or  liquid  asphalt. 

For  success  in  the  use  of  tar,  its  quality  is  most  important. 
If  it  is  heated  too  much  and  "refined"  too  far,  it  becomes 
brittle  and  makes  black  dust.     If  not  refined  enough,  the  light- 
oils  and  ammonical  liquors  will  disintegrate  it.     A  reliably 
uniform  product  is  essential.     Good  tar,  properly  applied,  is 
the  cheapest  and  best  form  of  dust-preventer  and 
road-saver,  being  more  effective  and  durable  than     Success  of 
any  other  now  known,  except  asphaltic  oil.     This     •     „ * 
decision  was  reached  by  the  Massachusetts  Highway 
Commission  after  a  year  of  use  and  careful  observation.     It 
also  accords  with  the  opinion  of  the  best-recognized  English 
and  French  authorities  on  road  construction. 

The  success  of  "tarviating"  depends,  however,  upon  the 
quality  of  the  tar,  which  must  be  the  best  possible;  the  state 
of  the  weather,  which  must  be  clear  and  warm;  the  condition 
of  the  road-surface,  which  must  be  clean  and  dry;  the  manner 
of  application,  which  must  be  rapid  and  complete. 

Too  much  tar  on  the  surface  will  be  worse  than  the  former 
mud  and  dust,  being  sticky  when  warm  and  slimy  when  wet; 
and  to  avoid  these  serious  objections  the  tar,  either  hot  or  cold, 
is  forced  in  a  fine  spray  into  the  minute  voids  and  spaces  be- 
tween the  stone  fragments,  by  means  of  pneumatic  pressure 
from  a  "tar-sprayer,"  by  which  the  quantity  and  the  distribu- 
tion are  made  uniform,  and  small  pools  of  tar  are  not  left  on 
the  surface.  Such  a  tar-sprayer  must  work  so  rapidly  that  full 
advantage  can  be  taken  of  warm,  dry  weather,  during  which 
to  treat  one-half  of  the  width  of  several  miles  of  road  per  day. 

From  this  it  will  be  realized  what  an  important  part  the 
tar-sprayer  plays  in  the  process  of  "  tarviating,"   and  why 
inventors    have    been    busy    devising    various    machines    for 
increasing  the  speed  and  decreasing  the  cost  of  application. 
Eight  machines  made  for  this  purpose  in  England      Tar_ 
and  France  were  subjected  to  a  competitive  trial,     spraying 
in     1907,    by    the     English    Roads    Improvement      machines. 
Association,    before    road-engineers     and     representatives    of 


234 


THE  ART  OF  ROADMAKING 


(From  Judson's  "Dust  Prevention.") 

FIG.  154. — Spreading  Tarvia  by  Hose  from  Tank.     (Michigan  Boulevard, 

Chicago.) 


(From  Judson's  "Dust  Prevention."') 

FIG.  155. — Spreading  Tarvia  from  a  Slotted  Sprinkler. 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST   235 

associations  from  all  parts  of    Great  Britain  as  well  as  from 
France,  Germany,  Italy,  and  Egypt. 

Some  of  these  machines  spread  both  hot  and  cold  tar  under 
pressure  through  spraying  nozzles,  giving  rapid  and  uniform 
flow  and  distribution  without  the  need  of  sweepers;  others 
distributed  hot  tar  by  gravity  and  spread  it  by  automatic  trail- 
ing brushes.  The  pneumatic  spreading  machines  are  each  very 
effective,  having  done  much  good  work  in  England  and  France, 
and  it  is  said  that  their  best  features  may  yet  be  combined  in 
one  machine.  Few,  if  any,  are  yet  used  in  the  United  States, 
where  distribution  is  still  made  by  slow  gravity  flow,  usually 
requiring  that  the  tar  be  heated  and  be  spread  by  hand- 
brooms,  at  high  cost  for  labor,  and  at  a  rate  of  progress  about 
one-twentieth  of  that  at  which  better  work  is  done  in  Europe. 

The  term  "  coal-tar"  is  very  indefinite,  the  products  of 
different  gas-works  varying  widely  with  the  kinds  of  coal  used 
and  the  methods  of  treatment,  each  of  which  is  frequently 
changed,  even  at  the  same  gas  works.  This 
knowledge  has  led  to  careful  tests  and  analyses 
of  different  types  of  coal-tar  to  determine,  if 
possible,  why  some  succeeded  and  others  failed  in  road  work. 
Treatments  have  been  made  by  experts  to  remove  objection- 
able components  and  those  which  would  be  soluble  in  rain- 
water, and  to  add  desirable  ones  which  might  increase  fluidity 
or  add  to  the  permanence  of  ductility  and  adhesiveness,  which 
should  be  such  that  after  boiling,  the  coal-tar  may  be  drawn 
out  in  long  threads.  Many  failures  which  had  formerly 
occurred  were  explained  by  the  former  omission  of  such  tests 
and  absence  of  such  qualities,  but  most  road  engineers  lack 
the  time  and  equipment  to  analyze  each  lot  of  tar,  or  to  inter- 
pret the  results  of  such  tests,  which  are  at  best  costly  and 
uncertain  and  are  of  little  general  utility  with  the  present 
knowledge  of  the  subject. 

There  can  be  no  successful  system  of  tarring  roads  unless 
there  is  available  a  uniform  standard  and  a  reliable  supply  of 
refined  tar.  The  lack  of  these  in  England  accounts  for  many 
failures,  and  has  so  far  prevented  the  universal  use  which 
would  be  expected  from  knowing  of  the  many  successes. 


236 


THE  ART  OF  ROADMAKING 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST   237 

-  Every  city  has  its  gas-works — often  several  of  them — each 
using  various  grades  of  coal,  and  frequently  changing  their 
methods  of  treatment  to  make  gas.  Even  when  these  features 
are  constant,  the  quality  of  crude  tar  from  a  given  supply- 
tank  will  vary  as  the  quantity  in  the  tank  varies,  the  tar  drawn 
from  the  bottom  of  a  full  tank  sometimes  differing  materially 
from  that  drawn  when  the  same  tank  is  nearly  empty.  The 
resulting  crude  coal-tars  are  therefore  produced  in  great  variety, 
so  that  road-construction  which  succeeds  at  one  time  may  fail 
at  another,  as  most  failures  have  resulted  from  the  use  of  poor 
tar. 

In  "tarviating"  experiments  in  the  United  States  some  very 
crude  appliances  have  been  used,  but  no  doubt,  as  the  im- 
portance and  demand  for  better  roads  increases,  there  will  be 
a  relative  improvement  in  the  mechanical  devices  used.  The 
number  and  the  variety  of  foreign  machines  for  rapidly  ap- 
plying tar  are  indications  of  the  general  recognition  of  the  need 
for  means  to  quickly  treat  great  lengths  of  roads  during  the 
short  periods  when  weather  conditions  are  favorable,  all  authori- 
ties agreeing  that  tar  should  only  be  applied  when  both  air 
and  road  are  warm  and  dry. 

Coal-tar  and   its  products  are  used  in  the  general  group 
of  pavements  called  tar-macadams,  composed  of  hot  crushed 
stone    and    specially    prepared    tar   or   bituminous 
cement,  mixed  while  hot  and  compressed  in  place.       ar~  . 
Of  this  group,  that  which  is  known  as  bitulithic 
pavement  seems  the  most  successful  for  streets,  and  in  lighter 
form  for  suburban  roads  and  the  interior  of  villages  and  small 
towns. 

There  is  a  considerable  difference  between  a  tar-macadam, 
and  tarring  a  macadam  road.  The  latter  is  a  surface  treat- 
ment while  the  name  "  tar-macadam "  is  applied  to  any 
crushed-stone,  or  crushed-slag  construction,  in  which  coal-tar, 
or  a  bituminous  cement,  or  a  material  containing  coal-tar 
or  bitumen,  or  both,  is  used  (instead  of  water)  in  binding 
the  filler  between  the  fragments  of  stone,  or  slag.  The  tar 
or  bitumen  remains  as  a  fixative  to  hold  in  place  the  stone 
chips,  screenings,  or  sand  forming  the  filler,  binder,  or  matrix 


238 


THE  ART  OF  ROADMAKING 


FIG.  157. — Finished  Macadam.     Untreated  portion  in  foreground. 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST  239 

for  the  fragments,  thus  aiming  to  better  the  road  (as  compared 
with  ordinary,  water-built  macadam)  by  excluding  water, 
reducing  wear  and  preventing  dust. 

Tar-macadam  may  consist  of  a  tarred  layer  only,  or  of  tar- 
ring all  the  fragments  in  the  entire  road,  either  before  spread- 
ing or  after  spreading  in  place  on  the  road. 

Any  good  form  of  the  cheaper  tar-macadams  costs  about 
one-third  more  than  the  ordinary  water-built  macadam  of 
the  same  kind  and  depth  of  stone,  because  of  the  added  cost 
of  the  tar  or  bituminous  cement,  the  necessary  restrictions 
as  to  working  only  in  warm  and  dry  weather,  and  also  the 
need  of  repairing  the  injuries  done  by  rain  coming  on  incom- 
plete work.  But  these  initial  increased  costs  are  offset, 
when  the  construction  succeeeds,  by  longer  life  of  the  road 
and  by  less  expense  for  cleaning,  maintenance,  and  repairs. 

When  good,  a  tar-macadam  road  is  practically  dustless 
and  noiseless,  offers  little  tractive  resistance,  and  endures  the 
passage  of  the  rubber  tires  of  high-speed  motor-cars;  and  as 
it  sheds  water,  it  is  not  heaved  nor  disintegrated  by  frost. 
It  has  the  disadvantage,  in  common  with  other  pavements, 
of  being  slippery  when  frosty. 

Tar-macadam  roadways  were  first  built  on  the  London  Road 
at  Nottingham,  England,  at  a  date  variously  stated  from  1840 
to  1845,  and  at  Sheffield  soon  after.  Other  similar  roads 
have  since  been  built  at  many  times  and  places  in  England 
and  in  France,  and  some  in  the  United  States  since  1900. 
The  earlier  ones  used  crude  coal-tar,  mixed  by  hand  with 
various  kinds  of  stone,  and  often  produced  failures  because  of 
the  poor  quality  of  the  crude  tar,  or  because  of  rain  or  cold 
during  construction.  Many  of  the  old  ones,  however,  are  still 
in  satisfactory  use,  as  well  as  many  new  ones. 

In  recent  years  the  necessity  of  having  properly  refined  tar 
has  become  generally  known,  and  improved  appliances  for 
heating  and  hand-mixing  the  tar  and  stones  have 
been  used  with  much  better  results  than  formerly 
as  to  cost  and  character;  the  mixing  has  been 
effectively  done  in  some  cases  with  an  ordinary  concrete 
mixer. 


240 


THE  ART  OF  ROADMAKING 


FIG.  158. — Petrolithic  Outfit  at  Work,  Ventura,  California. 


FIG.  159, — Petrolithic  Pavement  through  the  Orange  Groves,  California. 

Grade  10°. 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST  241 

Steam-operated  machines  have  been  produced  which  me- 
chanically heat  and  mix  stones  and  tar,  preparatory  to  spread- 
ing it,  cold,  upon  the  roads.  The  tar-spraying  machines  and 
tar-spreading  machines  adapted  to  tarring  the  stone  in  placer 
after  it  has  been  spread  on  the  road,  have  not  as  yet  been 
much  used  for  making  tar-macadam,  but  for  which  they  are 
well  suited,  although  the  methods  of  construction  have  been 
very  radically  improved  since  1905. 

The  "Gladwell"  system  is  a  method  of  surfacing  macadam 
roads,  either  old  or  new  ones,  with  a  tar-macadam  top  which 
gives  some  of  the  effects  of  tar-macadam,  and  at  a  less  cost. 
It   consists   in   imbedding   a   two-stone    course   of 
untarred,  clean,  crushed  stone  in  and  between  two  The 
layers  of  tarviated,  dustless  stone  chips,  forming  svstem 
a   matrix   which   is   worked,   by  judicious   rolling, 
into   the   spaces   between   the   stone   fragments   from   below 
upward  and  from  above  downward,  finally  sealing  the  surface 
so  as  to  be  waterproof  by  hot  tarvia  and  granite  chippings. 

The  system  was  devised  by  Arthur  Gladwell,  who  has 
charge  of  road  construction  and  maintenance  at  Eton,  near 
Windsor,  England,  and  was  first  used  by  him  in  July,  1906. 
It  has  since  been  successfully  used  on  the  roads  along  the 
Thames,  and  elsewhere  in  England.  Its  low  cost  and  ease 
of  construction,  and  especially  the  fact  that  most  of  the  work 
may  be  done  in  ordinary  weather,  will  no  doubt  lead  to  its 
extensive  use  in  the  United  States. 

There  is  as  yet  no  general  use  of  tar-macadam  on  rural 
roads  of  the  United  States  and  Canada,  such  work  having 
been  done  only  on  a  small  scale  in  an  experimental 
way  by  the  road  departments  of  some  of  the  States,  Use  of  tar~ 
and  by  a  few  towns  and  villages.     The  use  of  the  Amex-io*11 
high-class    bitulithic    and    similar    pavements    has 
been  confined  to  urban  and  suburban  streets.     The  United 
States  Office  of  Public  Roads  has  done  some  useful  work  at 
Jackson,  Tennessee,  and  the  results  as  published  have  been 
generally  read  and  used  as  the  basis  for  other  experiments. 
The  report  says: 

"  A  tarred  street  is  dustless  in  the  same  sense  that  an  asphalt 


242 


THE  ART  OF  ROADMAKING 


FIG.   160. — Spike  Disc  Harrow,  used  for  pulverizing  clods  and  mixing 
oil  in  Petrolithic  pavement  construction. 


FIG.  161— Roller  Tamper. 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST    243 

street  is  dustless,  though  a  fine  sandy  powder  wears  off  as 
in  the  case  of  asphalt.  In  driving  over  a  tarred  macadam 
road,  the  lessening  of  vibration  and  noise  is  at  once  noticeable. 
The  ordinary  macadam  produces  a  constant  succession  of 
slight  jars  upon  a  steel-tired  wheel  and  there  is  a  relief  felt 
at  once  in  driving  upon  a  road  treated  with  tar." 

The  Office  of  Public  Roads  continued  to  give  special 
attention  to  the  subject  during  1908  and  1909,  and  expressed 
the  opinion  that  surface  tieatments  were  palliatives  rather 
than  dust-preventives,  and  that  a  more  lasting  method 
would  be  "the  use  of  well-tarred  sand  as  part  of  the  binding 
material  and  to  fill  voids,"  applying  a  layer  of  such  tarred 
sand  to  the  rolled  base-course,  over  which  the  top  course 
should  be  spread  and  rolled  until  the  tarred  sand  should  work 
down  into  the  base-course  and  up  into  the  top-course.  The 
surface  being  then  finished  by  an  application  of  tar  covered 
with  fine  chips  or  sand  and  rolled  until  smooth  and  uniform. 
This  suggested  method  is  practically  the  same  as  the  "Glad- 
well"  system. 

Rock    asphalt   macadam    construction   gives   good    results, 
but  the  cost  of  transportation  has  limited  its  use 
to  the  vicinities  of  the  natural  formations  of  the    R°ck  as 
peculiar    sandstones    and    limestones    which    are      fam 
impregnated    with    bitumen    and    are    known    as 
"rock-asphalts." 

The  natural  formations  which  occur  in  Arkansas,  Oklahoma, 
and  Kentucky,  are  sand-rock  impregnated  with  a  proportion 
of  bitumen  varying  from  a  trace  to  a  maximum  of  thirteen 
per  cent,  six  per  cent  being  about  the  least  useful  proportion. 

The  European  supplies  are  those  of  France,  Sicily,  and 
Switzerland,  and  are  bituminous  limestones  formed  by  natural 
combinations  of  about  twelve  per  cent  of  bitumen  with  about 
eighty-eight  per  cent  of  amorphous  carbonate  of  lime,  and 
were  first  used  for  roads  in  Paris  in  1854,  and  since  then  have 
made  the  comparatively  small  extents  of  asphalt  pavements 
in  European  cities,  being  too  costly  for  general  use  and  much 
more  slippery  than  the  similar  city  pavements  made  from  the 
American  sand-rock  asphalts. 


244 


THE  ART  OF  ROADMAKING 


For  less  costly  roadways  in  the  cities  of  the  southwestern 
portion  of  the  United  States,  sand-rock  asphalts  from  the 
formations  in  Arkansas  and  Kentucky  have  been  combined 
with  ordinary  macadam,  making  a  pavement  that  is  not 
slippery  because  the  fragments  of  stone  imbedded  in  the 
ground  sand-rock  asphalt  give  a  good  foothold,  but  which 
needs  considerable  care  and  which  must  be  kept  clean. 

The  bitulithic   pavement   is  the   best   known   combination 


(From  Judsoris  ''City  Roads  and  Pavements."} 

FIG.  162. — Laying  Bitulithic  Pavement,  Toronto,  Ont. 


of  crushed  stone  and  bituminous  binder,  and  is  composed  of 
fragments  of  stone  which  are  held  firmly  and  free 
pavement  ^orm  attrition,  and  hence  form  no  dust.  It  differs 
from  other  bituminous  macadams  in  that  the 
proportions  of  the  several  sizes  of  fragments  of  crushed  stone, 
from  two  inches  in  size  down  to  dust  (which  form  about 
nine-tenths  of  the  final  mass),  are  accurately  determined  and 
are  so  combined  in  such  proportions  of  the  six  or  more  sizes 
that  the  final  voids  between  the  fragments  after  rolling  do 
not  exceed  10  per  cent,  or  less  than  half  the  ordinary  voids 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST  245 

in  rolled  stone.  This  puts  the  fragments  into  actual  and 
firm  contact,  so  that  the  addition  of  10  to  12  per  cent  by 
weight  (12  to  16  per  cent  by  bulk)  of  bituminous  compound 
fills  the  remaining  voids  and  makes  a  solid  and  impervious 
mass.  This  result  requires  experienced  care  and  skill  in 
selecting  and  combining  the  best  materials,  including  testing 
and  analyzing  the  components  of  the  bituminous  cement. 
The  pavement  thus  produced  is  one  which  water  cannot 
penetrate,  and  it  supports  the  passage  of  heavy  and  high- 
speed vehicles  without  any  loosening  of  the  bituminous  filler 
and  without  abrasion  of  the  fragments  of  stone,  so  that  no 
dust  comes  from  the  pavement  or  its  materials. 

With  the  present  general  knowledge  of  this  form  of  pave- 
ment which  has  been  acquired  since  1901,  opinions  are  now 
of  less  moment  than  in  its  first  years  o<  use,  but  the  general 
opinion  of  the  leading  authorities  is  substantially  that  ex- 
pressed by  the  Massachusetts  Highway  Commission: 

"The  bitulithic  pavement  is  undoubtedly  the  best  form 
of  pavement  to  give  the  desired  results  (durability  and  free- 
dom from  dust  under  fast  motor-car  travel),  but  it  is  too  ex- 
pensive for  many  locations." 

It  was  first  used  in  1901  in  Pawtucket,  R.  I.,  where  it  was 
laid  on  a  12  per  cent  grade,  and  during  the  same  year  sample 
areas  were  built  in  seven  cities,  aggregating  about  one  mile  of 
30-foot  width.  The  success  was  immediate,  and  the  use  in- 
creased each  succeeding  year,  so  that  at  the  close  of  1907, 
6,500,000  square  yards,  equal  to  422  miles  of  30-foot  road- 
ways, had  been  laid  in  one  hundred  and  sixty-six  cities  of 
the  United  States  and  Canada,  including  cities  in  the  region 
of  extreme  cold,  as  at  Edmonton,  Province  of  Alberta,  Canada, 
and  Glace  Bay,  Nova  Scotia,  and  in  the  South  at  El  Paso, 
Texas,  and  at  Atlanta,  Georgia.  This  widespread  success 
has  induced  imitations  and  consequent  litigations,  which  are 
further  evidences,  if  such  were  needed,  of  the  merits  of  the 
construction. 

The  elaborate  outfit  of  laboratory  and  machinery  and 
skilled  direction  required  to  successfully  produce  this  pave- 
ment would  at  first  seem  to  limit  construction  to  the  vicinity 


(From  Judson's  "Dust  Prevention.") 

FIG.  163. — One-car  Portable  Bitulithic  Railroad  Plant.     (Set  up  ready 

for  operation.) 


(From  Judson's  "Dust  Prevention.") 
FIG.  164. — Semi-Portable  Bitulithic  Paving  Plant. — End  view.      246 


THE  CONTROL  AND  PREVENTION  OF  ROAD  DUST  247 

of  permanent  plants,  and  this  idea  is  strengthened  by  visit- 
ing such  a  plant  and  examining  the  work  in  progress.  There 
have,  however,  been  built  and  patented  a  number  of  "semi- 
portable  bitulithic  paving-plants,"  each  permanently  set 
upon  a  platform-car.  These  outfits  make  it  possible  to  build 
this  pavement  in  many  widely  distant  places  and  to  give  to 
all  of  them  equally  reliable  results.  The  accompanying 
illustrations,  showing  this  semi-portable  bitulithic  paving-plant, 
are  lettered  to  accord  with  the  following  key : 

A.  Boiler  and  engine. 

B.  Rotary  driers  for  heating  and  drying  stone. 

C.  Elevators  for  delivering  the  stone  to  the  driers. 

D.  Elevators  for  conveying  the  heated  stone  to  the  sep- 

arating-screens. 

E.  Sectional  screen  for  separating  the  stone  into  several  sizes. 

F.  Sectional  bins  for  storing  the  several  sizes  of  stone  after 

separation,  and  delivering  same  to  the  weighing-box. 

G.  Weighing-box  resting  on  a  multiple  seven-beam  scale  for 

accurately  weighing  each  size  of  stone  in  predeter- 
mined proportions  and  delivering  same  into  the  mixer. 

H.  Twin  pug  mechanical  mixer,  having  two  shafts  revolving 
in  opposite  directions  with  arms  or  blades  inter- 
locking each  other. 

I.  Mixing  platforms  under  which  wagons  back  for  taking 
the  bitulithic  mixture  as  delivered  from  the  mixer. 

J.    Ogee-bottomed  bitumen-melting  tanks. 

K.  Bitumen  weigh-bucket  conveyor  and  dial-scale,  so  ar- 
ranged as  to  indicate  both  gross  weight  and  tare. 

L.  Rotary  exhaust  fan  for  providing  induced  draft  to  the 
rotary  driers. 

M.  Dust-separator  for  reclaiming  dust  drawn  by  the  exhaust 
fan  from  the  stone  while  it  is  drying. 

N.  Steel  frame  for  supporting  the  mixing-platform,  mixer, 
scale,  sectional  hot-stone  bin,  and  sectional  screens. 

O.  Steel  car  on  \vhich  the  semi-portable  or  railroad  plant 
is  permanently  set. 


CHAPTER  XII 
STATE   AID    LAWS* 

MOST  of  the  state-aid  laws  are  accumulations  of  laws  and 
amendments  passed  session  after  session  without  definite 
logical  arrangement,  and  without  any  carefully  thought  out 
general  plan  in  mind.  New  York,  however,  appointed  a 
special  commission  which  studied  the  question  very  carefully 
for  a  year,  both  in  their  own  state  and  in  neighboring  states. 
This  commission  proposed  a  bill  which  was  passed,  and  went 
into  effect  in  January,  1909.  This  bill  replaces  all  previous 
highways  law,  and  rearranges  the  whole  highway  work  of 
the  state,  counties  and  towns  so  as  to  bring  the  separate  units 
into  logical  relations  to  each  other. 

As  a  result  of  the  study  of  the  different  state  laws,  a  model 
bill  providing  for  state  aid  was  drawn  up  by  the  United  States 
Office  of  Public  Roads  at  Washington,  D.  C.,  to  embody  the 
best  results  of  the  experience  of  all  of  the  states  based  on  the 
workings  of  each  of  the  state  aid  laws  under  their  local  con- 
ditions. 

Briefly  stated,  the  three  things  that  are  most  fundamental 
for  the  successful  working  of  state  aid  are:  (1)  an  equitable 
plan  for  distributing  funds;  (2)  putting  the  spending  of  the 
money  in  the  hands  of  expert  men;  (3)  providing  for  such  a 
form  of  commission  that  the  work  will  be  carried  on  without 
regard  to  political  considerations. 

On  looking  over  the  summaries  of  the  state  aid  laws,  it  will 
be  found  that  the  various  states  pursue  a  variety  of  methods 
in  distributing  the  aid  to  the  localities  where  it  is  used.  Some 
states  leave  this  matter  entirely  in  the  hands  of  the  com- 

*  Abstracted  from  First  Biennial  Report  of  the  Highway  Division, 
Wisconsin  Geological  and  Natural  History  Survey,  1909. 

248 


STATE  AID  LAWS  249 

mission,  or  limit   the   commission  only  by   stating  that    not 
over  a  certain  maximum  or  not  less  than  a  certain 
minimum  amount  shall  be  spent  in  any  county.    One  Distribution 


state    divides    the    amount    equally    between    the  * 


counties;  another  divides  the  money  between  the 
counties  on  the  basis  of  the  total  number  of  miles  of  road  in 
each  county;  other  states  divide  the  money  in  proportion  to 
the  county  ;  other  states  divide  the  money  in  proportion  to  the 
amounts  asked  for,  so  that  if  the  aggregate  of  the  amounts 
of  state  aid  petitioned  for  is  twice  that  which  the  legislature 
has  appropriated  for  the  purpose  each  town  or  county  peti- 
tioning receives  one-half  of  what  it  asked  for. 

On  account  of  the  almost  necessarily  inequitable  manner  in 
which  taxes  are  generally  assessed  upon  property,  it  will  be 
very  evident  that  the  distribution  of  the  fund  must  become 
more  or  less  inequitable  in  certain  particular  cases. 

In  the  first  place,  the  method  of  leaving  the  distribution  of 
the  money  entirely  in  the  hands  of  a  commission  is  distinctly 
inadvisable,  as  it  puts  altogether  too  much  responsibility  on 
a  very  small  group  of  men,  whose  knowledge  of  conditions, 
even  though  they  may  be  ever  so  well  intentioned,  would 
hardly  be  broad  enough  to  qualify  them  to  do  justice  to  all 
the  counties  and  to  the  several  hundred  towns  in  any  large 
state. 

To  divide  the  money  equally  among  the  counties  would  be 
very  markedly  wrong,  as  counties  with  a  comparatively  scat- 
tered settlement  would  receive  as  much  as  large,  well-settled 
counties. 

To  divide  tne  money  on  the  basis  of  the  total  number  of 
miles  of  road  in  each  county  would  also  be  inequitable,  as  some 
of  the  less  wealthy  and  less  populous  counties  might  have  as 
many  or  even  more  miles  of  road  per  square  mile  of  area  than 
some  of  the  wealthier  and  more  settled  counties. 

To  divide  the  money  pro  rata  with  the  amounts  asked  for 
would  do  injustice  in  that  counties  which  are  able  to  ask  for 
large  sums  might  prevent  poorer  counties  able  to  ask  for  only 
very  small  sums  from  getting  their  proper  share.  For  instance, 
one  county,  which  is  neither  large  nor  wealthy,  might  petition 


250  THE  ART  OF  ROADMAKING 

$1000  of  state  aid.  Another  county,  comparatively  populous 
and  wealthy,  might  ask  for  $40,000  or  $50,000  a  year.  If  the 
total  amount  of  state  aid  asked  for  were  twice  the  state 
aid  appropriation,  the  former  county  would  only  get  $500 
where  it  should  have  had  $1000,  while  the  latter  would  get 
$20,000  where  in  justice  it  might  only  have  been  given 
$15,000. 

The  idea  of  the  most  jus't  apportionment  of  the  state  aid 
fund  that  first  occurs  to  anyone  studying  the  question  is  a 
distribution  on  the  basis  of  valuation.  Such  a  distribution, 
however,  presents  difficulties  in  that  the  amount  of  state  aid 
given  to  some  of  the  poorer  counties  would  not  be  sufficient 
to  amount  to  anything  unless  an  exceedingly  great  state  aid 
fund  were  appropriated. 

The  second  important  point  to  which  attention  should  be 
directed  is  the  final  authority  in  the  supervision  of  the  actual 
construction.  It  will  be  noticed  by  the  summary 
Supervision  of  the  state  laws  that  follows,  that  every  state 
struction  giving  state  aid  gives  authority  to  its  state  highway 
officers  to  say  what  methods  of  work  shall  be 
pursued  and  how  the  roads  shall  be  constructed.  This  matter 
is  important  because  it  has  to  do  with  the  primary  purpose 
of  state  aid;  that  is,  to  secure  efficient,  well-planned  work 
on  our  highways,  and  the  careful  expenditure  of  the  state 
aid  money,  instead  of  the  haphazard  work,  entirely  lacking 
in  plan,  which  is  secured  under  the  present  system. 

In  order  to  get  efficient  spending  of  our  road  money  we  must 
profit  by  the  experience  of  other  countries.  In  France  the 
best  engineers  that  their  colleges  produce  are  taken  into  the 
Department  of  Roads  and  Bridges,  and  the  state's  money  is 
spent  under  their  direction.  If  we  are  to  build  the  best  roads 
with  least  cost  we  must  have  efficient  engineering  departments 
in  charge  of  the  work  with  authority  to  say  that  the  best 
methods  only  shall  be  used.  In  order  that  such  an  engineer- 
ing force  might  not  be  so  large  as  to  be  unwieldy,  and  to  pro- 
mote economy,  it  should  be  provided  that  it  should  work, 
in  so  far  as  possible,  through  competent  county  highway  com- 
missioners. But  in  order  to  secure  efficiency  and  uniformity 


STATE  AID  LAWS  251 

in  the  work  the  final  authority  should  rest  in  the  state  engineer- 
ing department. 

One  of  the  most  important  questions  to  be  considered  in 
framing  a  state  aid  law  that  will  work  successfully  is  the  form 
of  the  state  commission  or  body  that  has  general 

control  of  the  work.     The  importance  of  this  point       m.of. 

commission, 
lies  entirely  in  whether  or  not  the  state  highway 

work  is  to  be  controlled  by  political  considerations  with  the 
resulting  inefficiency  of  the  actual  road  building,  or  whether 
it  is  to  be  controlled  entirely  in  the  interest  of  efficient  road 
work  without  regard  to  political  considerations.  Of  course 
no  one  would  say  anything  else  than  that  this  work  must 
be  kept  out  of  politics.  But  there  is  great  danger  that  po- 
litical influences  may  creep  in  as  they  nearly  always  do,  under 
the  guise  of  cheapness  or  efficiency  of  administration.  For 
this  reason  the  following  statements  deserve  particular  atten- 
tion from  everyone  interested  in  the  success  of  the  state  aid 
movement. 

A  study  of  the  laws  of  the  various  states  reveals  the  fact 
that  there  are  four  distinct  plans  for  the  control  of  the  state 
highway  department. 

1.  One  state  highway  commissioner  or  engineer  appointed 
by  the  governor  for  a  definite  term  of  years.     Five  states  have 
this  plan. 

2.  A  commission  of  three  men  paid  for  their  full  time  and 
appointed  by  the  governor  for  a  definite  term  of  office.     Two 
or  three  states  have  this  type  of  board. 

3.  A  commission  appointed  by  the  governor  for  a  definite 
term  of  office,  but  serving  without  pay  and  giving  only  general 
direction  to  the  work,  which  is  under  the  active  direction  of  a 
state  engineer  selected  and  hired  by  them  for  a  period  coin- 
cident with  satisfactory  service.     This  and  the  fourth  method 
are   analogous  to   a  business   corporation   with  its  board   of 
unsalaried  directors  and  the  general  manager  carrying  out  the 
details  of  the  general  policies  laid  down  by  them.     Six  states 
have  boards  of  this  kind.     These  states  get  able  men  of  wide 
experience  and  good  business  ability  to  serve  on  their  com- 
missions. 


252  THE  ART  OF  ROADMAKING 

4.  An  ex-officio  board  such  as  is  recommended  in  a  model 
state  aid  bill  by  the  United  States  Office  of  Public  Roads 
for  the  particular  purpose  of  avoiding  politics  in  the  state 
aid  work.  That  bill  makes  the  professors  of  civil  engineering 
in  three  different  colleges  members  of  the  state  highway  board 
by  virtue  of  their  position.  Such  a  commission  maintains 
its  existence  without  regard  to  what  particular  man  holds 
one  of  these  professorships.  It  need  not  be  made  in  this 
way,  however,  but  could  be  composed  of  the  holders  of  any 
non-political  positions  either  in  state  employ  or  otherwise, 
and  the  same  freedom  from  politics  enjoyed.  Seven  states 
have  this  form  of  commission.  In  no  one  of  them,  so  far  as 
information  is  available,  has  politics  become  a  factor  in  the 
state  road  work,  but  the  same  cannot  be  said  of  states  having 
other  forms  of  commissions. 

DIGEST  OF  STATE  AID  LAWS 

In  the  following  digest  of  the  laws  of  various  states,  the 
states  considered  are  not  all  of  those  providing  for  state  aid 
for  road  building,  but  are  sufficient  in  number  to  give  a  fair 
idea  of  the  various  methods  used  in  all  states.  The  states 
whose  laws  are  summarized  are: 

New  York  New  Jersey 

Maryland  Washington 

Virginia  Ohio 

Massachusetts  Michigan 

Connecticut  Maine 

Pennsylvania  Rhode  Island 

In  order  to  make  it  as  easy  as  possible  to  compare  the  pro- 
visions of  the  laws  they  are  grouped  under  various  headings. 
These  headings  are: 

State  Highway  Department. 
State  Aid  Highways. 
State  Aid  Fund. 
Powers  and  Duties  of  Counties. 
County  or  District  Highway  Engineers. 
How  Localities  get  State  Aid. 
Construction  of  State  Aid  Highways. 
Payment  for  State  Aid  Highways. 
Maintenance  of  State  Aid  Highways. 


STATE  AID  LAWS  253 


STATE  HIGHWAY  DEPARTMENT 

In  the  model  bill  of  the  United  States  Office  of  Public  Roads 
the  state  highway  commission  is  made  up  of  the  professors 
of  civil  engineering  in  three  different  colleges.  A 
commission  of  this  kind  was  selected  for  the  ex-  Model  bill, 
press  purpose  of  avoiding  political  influences  in 
the  work.  These  commissioners  receive  no  salary,  but  are 
paid  their  actual  expenses  in  attending  meetings,  etc.  They 
exercise  general  supervision  over  the  state  highway  work, 
appoint  the  state  engineer  to  hold  office  during  satisfactory 
service,  and  fix  his  salary.  This  engineer  has  charge  of  all 
the  state  road  work  and  appoints  his  engineering  assistants 
and  clerical  force,  subject  to  the  approval  of  the  commission. 
The  state  engineer  may  be  consulted  by  county,  city  or  town 
officers  concerning  roads  and  bridges. 

Xew  York  has  a  state  highway  department  in  charge  of 
three  commissioners  appointed  by  the  governor  for  a  term 
of  six  years,  one  of  them  going  out  of  office  every 
two  years.  One  of  these  commissioners  must  be  New  York, 
a  practical  civil  engineer  with  experience  in  the 
construction  of  highways  and  bridges.  The  chairman  of  the 
commission,  who  is  designated  by  the  governor,  is  paid  $6000 
a  year  and  the  other  two  commissioners  $5000  a  year  each. 
This  commission  has  general  supervision  over  all  state  aid 
work.  They  appoint  a  chief  road  engineer,  a  chief  bridge 
engineer,  and  such  clerks  and  assistants  as  are  needed.  This 
commission  apportions  the  state  highway  money  among  the 
various  counties  of  the  state  in  a  manner  they  think  equitable. 
They  have  authority  to  regulate  the  digging  up  for  any  pur- 
pose of  any  road  built  with  state  aid,  and  are  instructed  to  aid 
in  promoting  highway  improvements  and  to  carry  on  exper- 
iments in  road  construction. 

This  state  has  put  the  general  supervision  of  its  highway 
work  in  the  hands  of  an  ex-officio  commission,  the  Geological 
Survey  Board.  The  commission  is  composed  of 
the  holders  of  the  following  positions:  Governor  Maryland, 
of  the  state ;  Comptroller  of  the  state ;  President  of 
Johns  Hopkins  University ;  President  of  the  State  Agricultural 
College.  This  board  receives  no  salary,  but  is  reimbursed  its 
actual  expenses  for  attending  meetings,  etc.  They  appoint 
the  chief  engineer  and  fix  his  salary.  They  allot  the  state  aid 
money  to  the  various  counties  of  the  state  as  petitioned  for, 
the  allotment  to  each  county  being  made  on  the  basis  of  total 


254  THE  ART  OF  ROADMAKING 

road  mileage.  The  chief  engineer  makes  the  surveys,  plans, 
and  specifications  for  roads  built  under  state  aid. 

The  state  highway  commission  is  an  ex-officio  board  com- 
posed of  the  professors  of  civil  engineering  at  the  University 
of  Virginia,  Virginia  Agricultural  and  Mechanical 
Virginia.  College,  and  the  Virginia  Military  Institute.  Under 
their  direction  is  the  state  highway  commissioner,  who  is  ap- 
pointed by  the  governor  for  a  six-year  term.  This  commis- 
sioner must  be  a  civil  engineer  well  versed  in  road  building, 
and  a  citizen  of  the  state.  His  salary  is  $3000  per  year.  The 
commission  serves  without  pay,  but  is  reimbursed  actual 
expenses  for  attending  meetings.  The  state  commissioner 
has  authority  to  hire  engineers  and  assistants.  The  commis- 
sion apportions  the  state  aid  money  in  proportion  to  the  amount 
of  state  taxes  paid  by  each  county.  This  state  also  aids  the 
counties  in  road  construction  by  loaning  them  its  convicts  to 
work  upon  the  roads. 

This  state  has  a  highway  commission  of  three  men  appointed 
by  the  governor  for  a  term  of  three  years,  one  term  ending 
each  year.  The  president  of  the  commission  receives 
Massacht  $3500  and  the  other  two  members  $2500  each  per 
annum.  This  commission  appoints  a  secretary  who 
is  practically  state  engineer,  and  fixes  his  salary.  They  exer- 
cise general  supervision  over  the  state  aid  work,  and  employ 
such  engineers,  clerks,  etc.,  as  are  necessary.  The  apportion- 
ment of  the  state  highway  fund  is  left  entirely  in  the  hands 
of  this  commission,  with  the  single  restriction  that  they  can- 
not build  more  than  ten  miles  of  road  in  any  county  in  a 
year.  The  commission  has  absolute  authority  over  the  dig- 
ging up  of  state  aid  roads  for  any  purpose.  They  can  pur- 
chase such  machinery  as  is  needed  in  the  building  of  state  aid 
roads. 

This  state  has  a  single  highway  commissioner  appointed 
by  the  governor  for  a  four-year  term  at  a  salary  of  $3000. 

Conn  cticut  ^n  Edition  ^°  n^s  salary  ne  is  provided  by  the 
'  state  with  a  touring  car  and  a  man  to  run  it  to 
assist  him  in  getting  about  the  state  in  connection  with  his 
duties.  The  commissioner  appoints  such  deputies  and  en- 
gineers as  are  needed  and  fixes  their  salary  with  the  provi- 
sion .that  the  total  limit  of  salaries  is  $25,000  a  year. 
The  commissioner  allots  the  state  highway  fund  among  the 
various  towns.  He  has  authority  to  purchase  stone  crushers 
and  loan  them  to  the  towns  in  the  state  desiring  them. 

This  state  has  a  highway  department  under  the  direction 
of  a  single  commissioner  paid  a  salary  of  $6500  per  annum  and 


STATE  AID  LAWS  255 

appointed  by  the  governor  for  a  term  of  four  years.     The  law 
specifies  that  this  commissioner  "  shall  be  a  competent 

civil  engineer  and  experienced  in  the  construction  ipsyi- 

v  ,  •  r  j    j>     r™  •  vama. 

and  maintenance  of  improved  roads.  This  com- 
missioner appoints  a  deputy  at  a  salary  of  $3600,  and  an  as- 
sistant deputy  at  $3000,  twelve  engineers  and  a  chief  drafts- 
man at  $2400  each  and  such  other  assistants  and  clerks  as  are 
needed.  Among  his  duties  are  the  promotion  of  highway  im- 
provement, the  regulation  of  the  digging  up  of  the  state  aid 
roads  for  any  purpose,  and  the  collection  of  information  re- 
garding road  building. 

This   state  has   one  highway   commissioner   appointed   by 
the  governor  for  a  term  of  three  years,  at  a  salary  of  $5,000 

Eer  annum.     No  qualifications  are  specified  in  the 
iw.     The  regulation  of  the  digging  up  of  state  aid 
highways   is   left   to    the    counties.     The  state  commissioner 
has  supervision  over  the  surveys  and  plans  for  state  aid  roads, 
and  the  location  of  roads  to  be  improved    must    meet   his 
approval.     He    has    authority    to    reject    all    unsatisfactory- 
road  contracts  which  the  county  boards  may  desire  to  enter 
into.     He  appoints  the  supervisors  on  all  work  done  on  state 
aid  roads,  both  in  construction  and  maintenance. 

This  state  has   a  highway  board   composed  of  the  state 
auditor,  the  state  treasurer  ex-officio,  and  the  highway  com- 
missioner, who  is  appointed  by  the  governor  for  a__ 
four-year  term  at  a  salary  of    $2500  per  annum. 
This  commissioner  must  be  an  experienced  civil  engineer.     He 
has   authority  to   appoint  needed   engineers   and   assistants. 
The  state  highway  board  apportions  the  state  money  among 
the  counties  and  lets  all  contracts  for  the  building  of  state  aid 
roads. 

There  is  a  single  state  highway  commissioner  appointed 
by  the  governor  for  a  term  of  four  years  at  a  salary  of  $2500. 
The  law  requires  him  to  be  a  competent  civil  en- 
gineer  with  experience  in  highway  construction. 
It  is  his  duty  to  instruct  and  assist  town  and  county  officers 
in  the  making  of  improved  roads,  and  to  collect  information 
and  make  tests  and  experiments  in  road  building.  The  loca- 
tion of  all  roads  to  be  improved  must  meet  his  approval  and 
all  contracts  for  their  improvement  are  let  by  him  in  the  name 
of  the  state.  He  appoints  his  assistants  and  inspectors  for 
the  state  aid  work. 

There  is  one  highway  commissioner  appointed  by  the  gov- 
ernor for  a  term  of  four  years  at  a  salary  of  $2500.      The  only 


256  THE  ART  OF  ROADMAKING 

qualification  specified  in  the  law  is  that  he  shall  be  a  citizen 
of  the  state.  He  has  authority  to  appoint  needed 
Michigan.  cierks  an(j  a  deputy  commissioner,  and  is  instructed 
to  hold  public  road  institutes  in  each  county,  at  which  the 
attendance  of  town  and  county  highway  officers  is  required. 
These  local  officers  draw  their  regular  pay  and  expenses  for 
attending  these  meetings.  The  state  commissioner  furnishes 
plans  and  specifications  for  roads  and  bridges,  and  allots  the 
state  aid  fund  to  the  towns  or  counties  petitioning.  He  has 
authority  to  refuse  to  allot  any  money  to  a  town  or  county 
which  does  not  maintain  its  state  aid  roads  properly.  When 
state  aid  roads  are  completed  it  rests  with  him  to  decide 
whether  or  not  they  have  been  well  enough  constructed  to 
merit  the  payment  of  the  state  money. 

There  is  one  highway  commissioner  appointed  by  the  gov- 
ernor for  a  term  of  four  years  at  a  salary  of  $2500;  he  must 
be  a  civil  engineer.  He  appoints  an  assistant,  who 
must  be  a  civil  engineer  also,  and  must  have  the 
further  qualification  of  being  experienced  in  road  building. 
He  also  appoints  his  clerks  and  stenographer.  It  is  his  duty 
to  advise  the  towns  on  road  and  bridge  construction,  to  ap- 
portion the  state  aid  money  in  accordance  with  the  law,  make 
all  surveys  for  the  improvement  of  state  aid  roads  and  determine 
the  location  of  the  roads  to  be  improved.  He  appoints  in- 
spectors for  the  work  under  progress.  Meetings  are  held  in 
each  county  once  a  year  by  the  highway  commissioner. 

This  state  has  a  board  of  five  members  appointed  by  the 

governor  for  a  five-year  term  of   office,   one    member  being 

Rh  d  appointed  each  year.     This  board  receives  no  salary, 

but  the  members  are  reimbursed  their  expenses  for 

traveling  done    in    connection  with    their    duties. 

They  have    complete    authority  over    the    state  roads,   and 

employ  such  engineers  and  let  such  contracts  as  they  see  fit. 


STATE    AID    HIGHWAYS 

This  provides  the  state  aid  highways  are  to  be  selected  by 
M  d  b'll  ^e  country  boards,  subject  to  the  approval  of 

the  state  highway  department. 

This  state  has  three  systems  of  roads:  (1)  roads  built  en- 
tirely at  state  expense,  which  are  selected  by  the  legislature; 
N  (2)  county  roads,  which  are  selected  by  the  county 

boards,  subject  to  the  approval  of  the  commission, 
50  per  cent  of  the  cost  of  which  is  paid  by  the  state,  35  per 
cent  by  the  county  and  15  per  cent  by  the  town;  (3)  local 


STATE  AID  LAWS  257 

roads,  which  are  aided  by  the  state,  but  receive  no  county  aid. 
The  state  pays  from  one-third  to  one-half  of  the  cost  of  the 
local  roads.  The  local  roads  to  be  improved  are  selected  by 
the  town  board  and  the  town  highway  superintendent,  sub- 
ject to  the  approval  of  the  commission. 

No  road  in  the  state  of  New  York  is  improved  with  the  as- 
sistance of  the  state  until  both  the  location  and  the  manner 
of  improvement  have  been  passed  upon  favorably  by  the 
commission. 

The  highways  to  receive  state  aid  are  selected  by  the  county 
commissioners  subject  to  the  approval  of  the  state  highway 
department.  If  the  county  commissioners  refuse 
to  act  in  regard  to  any  road  the  owners  of  two-  ar7an  • 
thirds  of  the  adjoining  lands  can  compel  them  to  petition  the 
state  highway  department  by  agreeing  to  pay  10  per  cent  of 
the  cost. 

The  state  aid  roads  are  selected  by  the  county  board,  but 
both  the  location  and  the  method  of  work  must       v<    .  . 
approved   by   the   state   commissioner   before   any 
state  money  is  granted. 

The  Massachusetts  law  provides  that  counties,   cities  and 
towns  may  petition  the  state  highway  commission 
for  aid.     The  location  and  manner  of  construction 
of  roads  must  be    approved  by  the    state  highway 
commission  before  aid  is  granted. 

The  highways  to  receive  state  aid  are  selected  by  the  state 
commissioner.     The  local  people  of  a  township  may  petition 
for  state  aid,  but  this  petition  is  general  and  the 
particular  road  to  be  improved  is  selected  by  the    OE 
commissioner,  who  is  directed  by  law  to  improve  only  the 
main  highways  leading  from  one  town  to  another. 

In  this  state  the  township  supervisors  or  coimty  commis- 
sioners desiring  state  aid  petition  the  state  highway  com- 
missioner, who  may  grant  the  petition  if  he  ap- 
proves  of  the  location.  The  kind  of  road  to  be 
built  rests  entirely  with  the  state  commissioner. 

Roads  to  be  improved  with  state  aid  are  selected  by  the 
county  boards,  who  may  also    adopt  as  a   state  highway  any 
road  which  has  been  previously  improved  without  „ 
state  aid.     The  location  and   kind  of  road  to  be 
built  must  have  the  approval  of  the  state  highway  commis- 
sioner before  state  aid  is  granted. 

This  state  has  four  kinds  of  roads:  (1)  state  roads  constructed 
entirely  by  the  state,  which  are  selected  by  the  legislature; 


258  THE  ART  OF  ROADMAKING 

(2)  state  aid  roads;    (3)    improved  roads  which  are  paid  for 

entirely  by  the  county;   (4)   town  roads  which  are 
Washington.  buih  b    th 


people  The  location  anc[  method 
of  improvement  of  state  aid  roads  must  have  the  approval 
of  the  state  highway  board  before  state  aid  is  granted. 

The  roads  to  be  constructed  by  state  aid  are  selected  by  the 

county  board.     If  the  county  board  does  not  act  the  owners 

of  51  per  cent  of  the  linear  frontage  may  petition. 

The  location  and  kind  of  road  to  be  constructed 

are  subject  to  the  approval  of  the  state   commissioner.     If 

more  petitions  are  made  in  one  year  than  there  are  funds 

available  the  state  commissioner  and  the  county  board  to- 

gether decide  which  shall  be  constructed  first. 

In  this  state  the  county  board  of  highway  commissioners 

selects  the  roads  to  be  built  with  state  aid.     After  the  road  is 

Michi    n       completed   the   state  highway   commissioner   must 

approve  the  method  of  construction  before  state 

aid  is  granted. 

The  roads  to  be  built  with  state  aid  are  selected  by  the 
.  towns  subject  to  the  approval  of  the  state  com- 

missioner. 

This  state  has  no  roads  which  are  built  with  state  aid.     The 

only  classes  of  roads  which  it  has  are  those  paid  for  entirely 

by  the  state,  which  are  selected  and  constructed 

Island  ^7  the  state  board,  and  the  local  highways,   con- 

structed and  maintained  by  the  localities  without 

any  state  assistance. 

STATE    AID    FUND 

This  bill  provides  that  the  money  shall  be  raised  by  a  gen- 
Model  bill  era^  ^ax  anc^  apportioned  according  to  the  as- 

sessed valuation  of  the  counties. 

The  state  aid  fund  in  this  state  consists  of  a  bond  issue  of 
$50,000,000.  It  is  apportioned  by  the  state  commission  among 
New  York  ^e  counties  "  equitably  and  without  discrimina- 

tion/7 taking  road  mileage  and  improved  roads 
into  consideration. 

The  state  aid  fund  is  made  up  of  a  general  appropriation 
of  $200,000  annually  and  a  five-million-dollar  bond  issue. 
Mar  1  nd  T^e  annual  appropriation  is  apportioned  by  the 

state  board  according  to  the  total  road  mileage. 
The  five-milliori-dollar  bond  issue  is  used  to  pay  the  whole 
cost  of  certain  state  roads  which  are  selected  by  the  state 
board. 


STATE  AID  LAWS  259 

The  state  aid  granted  by  Virginia  is  in  two  forms.     They 
loan  state  convicts  to  the  counties  and  have  an  appropria- 
tion of  $25,000  for  the  transportation  and  caring  . 
for  these  men.     They  also  have  an  annual  money 
aid  appropriation  of  $250,000,  with  a  separate  appropriation 
of  $16,000  for  the  support  of  the  state  highway  commission. 
In  addition  10  per  cent  of  the  state  aid  fund  may  be  used  for 
the  necessary  engineering  on  the  roads  under  construction. 

The  state  aid  is  apportioned  by  the  commission  on  the  basis 
of  the  amount  of  state  taxes  paid  by  each  county.  If  any 
county  does  not  apply  for  its  share  it  is  divided  among  other 
counties  asking  for  more  than  is  first  apportioned. 

The  state  fund  of  this  state  is  made  up  of  an  annual  ap- 
propriation of  $450,000,  with  a  separate  appropriation 
of  about  $40,000  for  the  support  of  the  commission, 
approximately  $60,000  received  from  automobile 
license  fees  which  is  used  in  maintaining  roads.  The  state  aid 
is  apportioned  by  the  commission  as  they  think  equitable  and 
under  the  restriction  that  not  over  10  miles  of  road  can  be 
built  in  a  single  township  in  one  year. 

The  state  aid  fund  is  made  up  of  an  annual  appropriation 
of  $750,000.     This  is  apportioned  by  the  state  commissioner 
under  the  limitation  that  not  more  than  $10,000  Conn 
can  be  spent  in  any  town  in  one  year. 

The   state   aid  fund  is   made   up   of   an   appropriation   of 
$2,000,000    for    1908.      This    is    apportioned    by    the    state 
commissioner  among  the  counties  in  proportion  to 
to  total  road  mileage.     Apportionments  not  called 
for  by  any  county  are   reapportioned    among  the 
counties  desiring  more  than  their  first  apportionment. 

The  state  aid  fund  is  an  annual  appropriation  of  $400,000. 
This   is   apportioned   among  the   counties   by  the  „ 
state  highway  commissioner. 

The  state  aid  fund  is  made  up  of  an  annual  tax  of  one-half 
mill  on  all  the  property  in  the  state.     This  is  used  for  the 
building    of    " state    aid"    roads.     "State    roads," 
which  are  paid  for  by  the  state  alone,  are  covered 
by   separate  appropriation  of  $225,000  for  the  year  1908.     The 
state  aid  fund  is  apportioned  to  the  counties  in  the  order  in 
which  petitions  for  the  improvement  are  received. 

The  state  aid  fund  is  an  appropriation  of  $158,000  annually. 
It  is  divided  equally  among  the  counties.     Counties  0h.Q 

which  have  previously  built  roads  at  their  own  ex- 
pense are  entitled  to  reimbursement  from  the  state  aid  fund. 


260  THE  ART  OF  ROADMAKING 

For  the  year  ending  June  30,   1909,  the  Michigan  appro- 
priation was  $150,000.     The  salaries  and  expenses  of  the  office 
of  the  state  highway  commissioner  were  paid  from 
;higan.      ^e  gtate  general  funcl  m  addition  to  this.     State 

aid  money  is  apportioned  among  the  towns  and  counties  on  the 
basis  of  work  done  in  the  order  in  which  the  applications  are 
received. 

The  state  aid  fund  is  an  annual  tax  of  one-third  of  a  mill 
on  all  the  property  in  the  state.     It  is  apportioned  to  the 
.  counties  by  the  state  highway  commissioner  on  the 

basis  of  total  road  mileage.  The  county  appor- 
tionment is  then  divided  among  the  various  towns  in  the  county 
:on  the  pasis  of  valuation. 

The  state  aid  fund  is  a  bond  issue  of  $600,000  for  the  two 

years    1907   and    1908.     It   is   apportioned   as   the 

state  board  sees  fit  within  the  limits  that  not  over 

one-third   nor   less  than   one-seventh  of   the   total 

amount  can  be  spent  in  one  county  during  the  year. 

POWERS    AND    DUTIES    OF    COUNTIES 

The  authority  of  the  county  board  ends  with  selecting  the 
.          road  and  paying  their  share  of  the  cost  of  construc- 
tion   and    maintenance;     both    construction    and 
maintenance  being  looked  after  by  the  state. 

In  this  state  the  county  board  may  levy  a  tax  for  permanent 
improvements.  They  may  borrow  money  in  anticipation 
New  York  °^  *axes-  They  must  provide  lands  for  the  right 
of  way  for  new  state  or  county  roads.  They  may 
elect  a  county  highway  superintendent  for  a  four-year  term, 
but  if  they  do  not  choose  to  elect  such  a  man  the  state  com- 
mission appoints  a  district  superintendent  over  a  number  of 
counties  and  the  county  is  then  obliged  to  pay  its  share  of  his 
salary.  The  removal  of  the  county  superintendent  of  highways 
is  in  the  hands  of  the  state  commission.  The  town  is  liable 
for  all  damages  due  to  defects  in  any  road. 

In  this  state  the  county  commissioners  petition  for  the 
road  improvement.  They  let  the  contract  for  the  construc- 
Ma  land  tion  of  roads  subject  to  the  approval  of  the  state 
board,  must  provide  lands  for  the  right  of  way  and 
relocation,  may  elect  a  county  highway  engineer,  and  must 
keep  the  state  aid  roads  in  a  condition  of  repair  satisfactory 
to  the  state  board. 

The  county  board  petitions  for  the  road  improvement,  and 
after  this  has  no  further  authority  or  responsibility  excepting 


STATE  AID  LAWS  261 

to  pay  their  share  for  the  construction  and  maintenance,  both 

of  these  being  in  the  hands  of  the  state  commissioner. 

The  county  engineer,  if  there  is  one  in  the  county, 

is  selected  by  the  state  highway  commissioner,  but  paid  by 

the  county  board. 

After  petitioning  for  state  aid  the  county  has  no 
further  authority  or  responsibility  excepting  to  pay 
for  its  share  of  the  cost. 

In  this  state  the  county  is  not  an  important  unit  of  gov- 
ernment, and  the  state  deals  only  with  the  towns. 
After  the  town  has  petitioned  for  state  aid  matters    OI1 
are  entirely  in  the  hands  of  the  state  commissioner. 

The  county  may  petition  for  the  improvement  of  a  road, 
and  may  enter  into  a  contract  with  the  state  to 
do  the  actual  work  of  construction.     The  county 
elects  a  county  highway  engineer,  and  is  responsible 
for  all  damages  due  to  defects  on  state  aid  roads. 

The  counties  may  raise  a  tax  for  the  construction  and  repair 
of  state  aid  roads  amounting  to  five  mills.  They  may  bond 
for  as  much  as  3  per  cent  of  the  assessed  valuation 
for  road  purposes.  Counties  have  the  authority  w  ->ersey- 
to  acquire  property  and  machinery  for  road  purposes.  They 
must  elect  a  county  supervisor  of  roads  as  soon  as  the  first 
state  aid  road  is  completed  in  that  county.  This  supervisor 
may  be  removed  by  the  county  or  by  the  state  commissioner. 
The  county  has  control  of  the  state  aid  roads  within  its  bound- 
aries and  must  keep  the  same  in  a  state  of  repair  satisfactory 
to  the  state  commissioner.  The  county  must  accept  as  a 
state  highway  any  road  built  by  the  local  people  in  a  manner 
approved  by  the  state  highway  commissioner.  The  county 
has  authority  to  regulate  the  digging  up  of  state  aid  roads  for 
any  purpose. 

The  counties  may  levy  a  four-mill  tax  for  road   improve- 
ment and  can  bond  to  the  amount  of  5  per  cent  of  the  valua- 
tion.    They  may  acquire  property  and  machinery 
for  road  purposes.     The  county  surveyor  must  be 
a  civil  engineer,  and  his  title  is  changed  by  the  highway  law 
to  county  engineer.     The  counties  must  maintain  the  state 
aid  roads  under  the  orders  of  the  state  commissioner. 

The  county  board  may  levy  a  tax  of  not  to  exceed  one  mill 
for  road  improvements  and  may  issue  bonds  to  pay 
for  state   aid    roads.     They  may    elect    a    county 
highway  engineer.     They  may  secure  lands  for  right  of  way 


262  THE  ART  OF  ROADMAKING 

and  must  maintain  the  state  aid  roads  in  a  manner  satisfactory 
to  the  state  commissioner. 

The  county  elects  by  popular  vote  a  county  board  of  high- 
way commissioners  of  not  over  five  men.  This  board  of  high- 
way commissioners  may  levy  a  tax  of  not  to  ex- 
Michigan.  CQQ^  ^WQ  m{\\s  for  permanent  improvements.  The 
counties  may  bond  up  to  5  per  cent  of  their  valuation,  and 
must  maintain  the  state  aid  roads  to  the  satisfaction  of  the 
state  commissioner  or  be  cut  off  from  further  state  aid.  The 
county  is  responsible  for  damages  due  to  defects  in  state 
aid  roads.  This  board  selects  the  system  of  county  roads  to 
be  improved  with  state  aid. 

The  county  boards  designate  the  roads  to  be  permanently 
improved  on  the  petition  of  the  towns,  subject  to  the  approval 
of  the  state  commissioner.  They  may  levy  a  tax 
Maine.  Qf  one_third  mill  for  improvements  on  state  aid 
roads.  This  amount  must  be  spent  under  the  direction  of 
the  state  commissioner.  Towns  may  raise  an  additional 
amount  if  they  want  state  aid. 

Rhode  This  state  does  not  deal  with  the  counties  at  all 

Island.          in  its  permanent  improvements. 

COUNTY    OR    DISTRICT    HIGHWAY    ENGINEERS 

County  engineers  are  appointed  by  the  state  engi- 

n  '     neer  on  the  approval  of  the  commission. 

The   county  board   elects  a  county  highway  engineer  for  a 

term  of  four  years  and  fixes  his  salary.     If  the  county  board 

does   not    choose    to    elect,    the    state    commission 

r  '     appoints  a  district  engineer  to  have  charge  of  the 

work   in   several   counties.     Each   of   these   counties   is   then 

obliged  to  pay  its  share  of  his  salary.     The  qualifications  of 

the  county  highway  engineer  are  set  by  the  state  civil  service 

commission,  and  only  those  who   have   passed  a  satisfactory 

examination  are  eligible.     His  duties  are  to  advise  with  towns 

and  village  officers,  have  charge  of  the  construction  of  new 

roads  in  his  county,  and  the  maintenance  of  all  state  aid  roads, 

and  such  other  duties  as  the  commissioner  or  the  county  board 

assign  to  him. 

The  county  engineer,  when  there  is  one,  is  appointed  by  the 
county  commissioners.  His  term  is  indefinite,  and  continues 
M  r  1  nd  W^  sa^^ac^ory  service.  The  law  specifies  that 
he  must  be  a  civil  engineer.  He  has  charge  of  all 
the  county  road  work,  and  the  local  road  superintendents  are 
under  his  direction. 


OF    THE 

UNIVERSITY 

Of 


STATE  AID  LAWS  263 

The   county  engineer  is  appointed  by  the  state  highway 
commissioner  and  the  law  provides  that  he  shall 
be  paid  at  not  to  exceed  the  rate  of  $1200  a  year       Virgini*. 
for  the  time  actually  employed.     He  must  be  a  civil  engineer. 

This  state  has  no  county  engineers,  but  the  state  commission 
appoints  division  engineers  to  have  charge  of  the 
work  in  each  of  the  five  divisions  of  the  state.     These    Massachu- 
engineers  are  paid  by  the  state   and  must  be  ex- 
perienced civil  engineers. 

This  state  has  no  county  or  division  engineers.     The  state 
highway    commissioner   and   his    assistants   do    all 
the  engineering  work,  usually  hiring  engineers  for Connectlcut- 
each  particular  job. 

The  counties  in  this  state  have  county  engineers 
who  make  plans    and    surveys  subject    to  the  ap-       Penpsyl- 
proval  of  the  state  commissioner. 

The  county  board  must  elect  a  county  supervisor  of  roads 
on  the  completion  of  the  first  state  aid  highway  in  that  county. 
His  term  is  three  years,  and  his  compensation  is 
fixed  by  the  county  board.  In  some  counties  the  ew  J61"86^' 
engineer  is  paid  as  much  as  $6000  a  year.  He  may  be  re- 
moved by  the  county  board  or  by  the  state  commissioner. 
He  has  charge  of  the  improvements  made  in  his  county  and  the 
maintenance  of  the  roads.  The  only  qualification  named  is 
that  he  shall  be  a  "  suitable  person." 

The  county  engineer  is  elected  by  popular  vote  for  a  two  year 
term.     His  salary  is  $5  per  day  for  time  actually  spent  on  the 
work  in  the  smaller  counties,  and  the  same  as  the 
county   auditor   in   large   counties.     The   law   pro- 
vides that  he  must  be  a  civil  engineer.     Among  his  duties  are 
the  keeping  up  of  a  county  road  map  and  the  preparation  of 
profiles  of  roads,   reporting  on  proposed   improvements  and 
supervising  the  road  work  done  in  his  county. 

It  is  optional  with  the  county  boards  to  elect  county  engi- 
neers.    The    state    highway   commissioner's    office, 
however,   does  practically   all  the  engineering  on 
state  aid  roads. 

They  have  no  county  highway  engineers  in  this  state,  but 
instead  have  a  county  board  of  highway  commissioners  elected 
by  the  people.     This  board  may  be  from  one  to 
five  men  as  the  county  board  chooses,  and  the  term 
depends  on  the  number.     One  man  goes  out  of  office  every 
two  years.     If  there  are  five  men  the  term  is  ten  years,  if  there 
are  three  men  the  term  is  six  years  and  so  on.     The  only 


264  THE  ART  OF  ROADMAKING 

qualification  named  is  citizenship  in  the  county.  This  board 
has  all  authority  over  county  roads.  Their  salaries  are  fixed 
by  the  county  board. 

They  have  no  county  or  district  engineers  in  this 
Maine-  state. 

Rhode  There  are  no  county  or  district  engineers  in  this 

Island.  state. 

HOW    LOCALITIES    GET    STATE    AID 

The  county  board  petitions  the    state  highway 
Model  bill,     department. 

The  county  board  petitions    the  state    highway 
Drk'     commission. 

The  county  board  petitions  the  state  highway  department, 
but  if  the  board  refuses  to  act  the  owners  of  two- 
Maryland,     thirds  of  the  adjoining  lands  may  force  the  county 
to  petition  by  agreeing  to  pay  10  per  cent  of  the  cost. 

The  county  board  petitions    the    state  highway 
Virginia.        commissioner. 

(  Counties,  cities  or  towns  may  petition  the  state 

highway  commissioner,  for  aid,  but  the  commission 
chusetts.  J  ..  „  ,,.  ,  V, 

has  practically  nothing  to  do  with  cities. 

The  towns  vote  money  for  road  improvement  and  petition 

the  state  highway  commissioner,  who  selects  the  road  to  be  im- 

proved.     If  a  town  fails  to  vote  money  to  improve 

:ut*  an  important  road  which  needs  it  badly  the  state 

commissioner  is  empowered  to  go  ahead  on  his  own  initiative 

to  improve  the  road,  and  the  town's  share  of  the  expense  is 

taken  out  of  any  subsequent  allotments  that  may  be  made  by 

the  state. 

The  town  petitions  the  county,  and  the  county  then  peti- 
tions the  state  commissioner.  Towns  may  petition  the  state 

commissioner  directly  if  they  are  willing  to  pay  the 
vania.Sy  ~  county's  share  of  the  cost  as  well  as  their  own. 

The  owners  of  a  majority  of  the  assessed  valuation 
of  the  real  estate  in  the  town  can  by  petition  compel  the  town 
board  to  request  the  county  board  to  apply  for  state  aid. 
The  petitioners  as  such  are  not  obliged  to  assume  any  part  of 
the  cost  of  building  the  road. 

The   governing   board   of   any   town,    county,    borough   or 

village    may   petition    the    state    highway    commissioner.     If 

the  property  owners  on  a  particular  highway  de- 

r*  sire  to  have  it  improved  and  the  officials  refuse  to 

act  they  can  improve  the  road  at  their  own  expense  and  the 


STATE  AID  LAWS  265 

county  board  is  obliged  to  accept  it  as  a  state  highway  and 
thereafter  maintain  it. 

The  county  petitions  the  state  highway  board.     The  owners 
of  two-thirds  of  the  property  on  any  road  may  com- 
pel   the   county  to  petition  for  improvements  on 
that  road. 

The  county  board  petitions  the  state  highway  commissioner 
for  aid,  and  if  they  do  not  act  voluntarily  the  own- 
ers of  51   per  cent   of  the  frontage  may  compel  Ohl0* 
them  to  act. 

The  town  or  the  county  may  petition  the  state  highway 
commissioner.     If  they  issue  bonds  and  build  several  miles 
of  road  in  one  year  they  receive  their  share  of  state 
aid  on  two  miles  of  this  road  each  year  until  they      Mlchlgan- 
receive  the  total  amount  of  state  aid  which  they  are  entitled  to. 

In  order  to  get  state  aid  the  towns  must  raise  an  extra  high- 
way tax   of   from    1-12   to  1-4   mill,  according   to 
the  valuation  of  the  town,  and  petition  the  state 
highway  commissioner.     If  he  approves  the  petition  the  road 
is  built. 

Rhode  Island  does  not  deal  with  the  localities  at 

all  but   builds   the   roads   directly  under   the  state 

Island, 
commission. 


CONSTRUCTION    OF    STATE    ROADS 

The  construction  is  in  the  hands  of  the  state  engineer,  who 
makes   plans,   surveys,   estimates,   etc.     The   machinery  nec- 
essary is  provided  by  the  state  and  its  operation  paid 
for  by  the  county.      All  work  costing  over  $2000  >llL 

is  let  by  contract.  The  state  engineer  lets  all  contracts  in  the 
name  of  the  state.  Partial  payments  on  work  in  progress  must 
not  exceed  85  per  cent  of  the  cost  according  to  the  engineer's 
estimate.  The  inspection  of  the  work  during  construction  is 
entirely  in  the  hands  of  the  state  engineer. 

Grades  and  width  of  improved  surface  are  fixed  by  the  state 
engineer. 

The  construction  of  state  aid  roads  is  entirely  subject  to  the 
state  commission.     Plans,  estimates    and    surveys  are  made 
under  their  direction  and  they  let  all  contracts  for 
work.     The  county  must  furnish  the  right  of  way 
for  relocations.     Towns  or  counties  may  bid  on  the  construction 
the  same  as  any  contractor,   and  if  they  are  low  bidders  the 
commission  lets  the  contract  to  them.     The  inspection  of  the 


266  THE  ART  OF  ROADMAKING 

work  during  construction  is  done  by  the  state,  and  if  the  work 
is  not  being  properly  carried  on  the  state  has  authority  to 
stop  it  and  relet  the  contract. 

Grades  and  width  of  improved  surface  are  fixed  by  the  state 
commission. 

The  construction  of  state  aid  roads  is  all  under  the  super- 
vision of  the  chief  engineer  of  the  highway  division.     Plans, 
estimates  and  surveys  are  made  by  him.  Contracts 
aryan  .      £or  wor]^  are  }e^  j^y  ^e  county  board  subject  to 

the  approval  of  the  engineer.  The  inspection  during  the 
progress  of  the  work  is  done  by  the  state. 

Grades  and  width  of  improved  surface  are  fixed  by  the  state. 
Plans,  surveys  and  estimates  of  state  aid  work  are  made 
by  the  state  highway  commissioner.     All  work  is  done  under 
.  .          contract  let  by  the  state  commissioner.     The  coun- 
irgmia.       ^-^  mav  ^-^  Qn  worji  jn  competition  with  other  con- 
tractors.    The  inspection  of  the  work  in  progress  is  done  by 
the  state  commissioner  or  some  of  his  assistants. 

Grades  and  width  of  improved  surface  are  fixed  by  the  state. 
The  work  of  building  state  aid  roads  is  in  the  hands  of  the 
state  highway  commission,  under  whose  direction  plans,  surveys 
and  estimates  are  made.     The  state  pays  for  a  new 
chuTetts        right  of  way  in  case  a  relocation  of  the  road  is 
necessary.     The  highway  commission  has  machinery 
which  it  loans  to  the  local  people.     All  contracts  are  let  by 
the  commission,  and  cities  or  towns  may  take  contracts  at 
the  estimate  of  the  commission  without  calling  for  competitive 
bids  on  the  work.     The  inspection  of  the  work  during  prog- 
ress is  done  by  the  state  commission. 

The  maximum  grade  allowed  is  6  per  cent.     Width  of  im- 
proved surface  is  fixed  by  the  state. 

Plans,  estimates  and  surveys  are  made  by  the  state  high- 
way commission.     Towns  may  submit  competitive  bids  for 
doing  the  work.     Contracts  are  let  by  the  state 
highway  commissioner,  and  inspection  of  the  work 
during  progress  is  made  under  his  direction. 

Grades  and  width  of  improved  surface  are  fixed  by  the  state. 
The  law  of  this  state  provides  that  all  state  aid  highways 
shall  be  built  according  to  the  standards  adopted  by  the  state 
highway  department.     This  department  gives  the 
roads   thorough    inspection    during   the   period    of 
construction.     The  law  provides  that  no  state  aid 
roads  shall  be  built  less  than  12  feet  wide.     Grades  are  fixed 


STATE  AID  LAWS  267 

by  the  state  commissions.  The  state  aid  work  is  done  under 
contracts  let  by  the  state  highway  commissioner.  Counties 
and  towns  may  bid  on  work  if  they  so  desire. 

In  this  state  the  surveys  and  plans  are  made  by  the  county 
engineer,  but  are  subject  to  the  approval  of  the  state  highway 
commissioner.  The  county  provides  the  right 
of  way  for  relocations.  All  work  is  done  by  con-  w  Jersey- 
tracts  let  by  the  county  board  subject  to  the  approval  of  the 
state  highway  commissioner.  The  state  inspects  the  roads  dur- 
ing their  construction. 

Grades  and  width  of  improved  surface  are  subject  to  the 
approval  of  the  state  commissioner. 

Plans  and  surveys  are  made  by  the  state  highway  commis- 
sioner. The  maximum  grade  must  not  be  over  5  per  cent  and 
the  width  of  improved  surface  must  not  be  less  than 
8  feet  nor  over  16  feet,  unless  the  locality  wishes Washington' 
to  pay  the  whole  cost  of  the  excess  width.  All  state  aid  work 
is  done  under  contracts  let  by  the  state  highway  commis- 
sioner. Counties  may  bid  on  these  contracts  if  they  so  de- 
sire. In  case  relocation  is  necessary  the  county  provides  the 
right  of  way.  The  county  engineer  inspects  the  roads  during 
construction  under  the  direction  of  the  state  highway  com- 
missioner. 

The  construction  of  state  aid  roads  is  in  charge  of  the  state 
highway   commissioner,  who  makes  all  plans,  estimates   and 
surveys.     The   width   improved   must   not   be   less 
than   8  feet   nor   greater   than   16   feet  unless  the  Ohio. 

locality  wishes  to  pay  the  cost  of  the  excess  width.  The  grades 
must  be  such  as  will  meet  the  approval  of  the  state  highway 
commissioner.  The  work  is  done  under  contracts  let  by  the 
state  highway  commissioner,  and  the  inspection  during  con- 
struction is  done  by  him. 

Surveys  for  improvements  to  be  made  with  state  aid  are  made 
by  the  county,  but  the  plans  must  be  submitted  to  the  state 
commissioner  for  his  approval.  The  county  or 
town  has  direct  charge  of  the  work,  but  the  state  Mlchlgan- 
inspects  it  carefully  when  completed.  The  Michigan  law  con- 
tains specifications  according  to  which  the  roads  must  be 
constructed  in  order  to  receive  state  aid.  All  work  is  let  by 
contracts  by  the  town  or  county  if  it  exceeds  $500  in  amount. 
No  grades  may  exceed  6  per  cent  and  the  width  of  improved  sur- 
face must  not  be  less  than  9  feet  in  order  to  receive  state  aid. 

The  work  of  improving  state  aid  highways  is  under  the  super- 
vision of  the  state  highway  commissioner.     His  force  inspects 


268  THE  ART  OF  ROADMAKING 

them  while  they  are  under  construction,  and  makes  the  plans 
and  surveys  before  construction  is  begun.     Work  is 

Maine.          done  under  contracts  which  are  let  by  the  towns  sub- 

ject the  approval  of  the  state  commissioner. 

Construction  is  in  charge  of  the  state  board,  who  make  all 
plans  and  surveys  and  let  contracts  and  do  the 
inspection  while  the  road  is  under  construction. 
The  law  provides  that  the  roads  shall  not  be  im- 

proved for  a  less  width  than  14  feet. 

PAYMENT    FOR    STATE    AID    HIGHWAYS 

The  state  pays  two-thirds  of  the  cost  in  the  poorer  counties 

and  one-half  in  the  richer  counties.     The  whole  cost  is  paid 

at  first  by  the  state  and  the  counties  repay  their 

'     share  to  the  state.     No  part  of  the  cost  of  the  im- 

provements is  assessed  on  abutting  property. 

On  county  highways  the  state  pays  50  per  cent  of  the  cost, 

the  county  35  per  cent  and  the  town  15  per  cent.     On  town 

roads  the  state  pays  from  33|  to  50  per  cent  and  the 

r  '     town  66f  to  50  per  cent,  depending  on  whether  the 

town  is  rich  or  poor.     The  county's  share  is  paid  to  the  con- 

tractor by  the  county  treasurer  and  the  state's  share  is  paid 

direct  to  the  contractor  by  the  state  treasurer.     New  York 

formerly  assessed   15  per  cent  on  abutting  property  owners 

if  they  originated  the  petition  for  the  improvement,  but  this 

assessment  has  been  done  away  with.     The  state  does  not 

pay  any  share  of  the  cost  of  bridges  exceeding  five  feet  in  length. 

The  county  first  pays  the  whole  cost  of  the  road  and  the 

state  repays  half  the   cost  to  the  county.     If  the  property 

owners  force  the  county  board  to  act  they  have  to 
ary  an  . 


and  the  state  50  per  cent.  All  bridges  on  the  highway  to  be 
improved  are  considered  as  part  of  the  highway  and  the  state 
pays  its  share  of  the  cost.  No  part  of  the  cost  is  assessed  on 
abutting  property  except  as  mentioned. 

The  county  treasurer  pays  the  contractor  on  the  certificate 
of  the  state  highway  commissioner.  The  state  treasurer  turns 
v.  .  .  the  state's  allotment  over  to  the  county  treasurer 
upon  the  certificate  of  the  state  highway  commis- 
sioner. The  state  pays  half  of  the  expense  of  the  permanent 
improvement  and  leaves  it  to  the  county  to  decide  how  much 
shall  be  borne  by  the  county  as  a  whole  and  how  much  assessed 
to  the  local  road  district.  There  is  no  provision,  however, 
for  an  assessment  of  the  cost  upon  the  abutting  property.  If 


STATE  AID  LAWS  269 

the  allotment  of  the  state  aid  fund  to  any  county  is  $2500  or 
less,  that  county  may  use  it  to  aid  in  paying  for  the  building 
of  permanent  bridges  under  plans  made  or  approved  by  the 
state  highway  commissioner.  The  county  must  put  in  an 
equal  or  greater  sum,  however,  so  that  the  state  does  not  pay 
more  than  half  the  cost  of  the  bridges. 

The  state  treasurer  pays  the  whole  cost  of  the  work  on  the 
order  of  the  highway   commission.     The   counties 
have  six  years  in  which  to  pay  back  to  the  state  one- 
fourth  of  the  cost.     No  part  of  the  cost  of  the  roads 
is  assessed  on  the  abutting  property  owners. 

The  state  pays  the  full  amount  to  the  contractors  and  the 
towns  afterward  pay  back  to  the  state  one-quarter  or  one-eighth 
of  the  cost,  depending  upon  the  wealth  of  the  town. 
None  of  the  cost  is  assessed  on  abutting  property.    OE 
Nothing  is  said  in  the  law  regarding  aid  for  bridges  on  state 
aid  roads. 

The  state  pays  three-quarters  of  the  cost  and  the  county  and 
town  each  one-quarter.     The  total  cost  is  first  paid 
by  the  state,  and  the  counties  and  towns  afterward        Vania 
pay  their  share  to  the  state  treasurer.     The  state 
pays  the  same  share  of  the  cost  in  building  bridges  that  it  pays 
for  building  roads.     No  part  of  the  cost  of  roads  is  assessed 
on  abutting  property. 

The  state  treasurer  pays  one-third  the  cost  of  the  roads  and 
the  county  teasurer  pays  the  contractor  on  the  estimates  of 
the  engineer.     Formerly  15  per  cent  was  assessed 
on  abutting  property,  but  now  no  part  of  the  cost     ew  Jer 
is  assessed  in  this  way.     New  Jersey  does  not  give  state  aid 
for  bridges. 

The  state  and  the  county  each  pay  half  of  the  cost  of  the 
state  aid  roads.     Each  treasurer  pays  direct  to  the  contractor 
on   vouchers  of  the   state  highway   commissioner 
Thirty-five  per  cent  of  the  cost  is  paid  from  thew 
county  funds,  and  15  per  cent  from  the  road  district  funds. 
If  the  property  owners  petition,  15  per  cent  is  paid  by  the  owners 
of  all  property  lying  within  a  half  mile  either  side  of  the  road. 
Nothing  is  said  in  the  law  about  state  aid  for  bridges. 

The  state  pays  25  per  cent,  county  50  per  cent,  the  town 
10    per    cent,    and    abutting   property    owners    15 
per  cent.     The  law  says  nothing  about  state  aid 
for  bridges. 

The  total  cost  of  the  road  is  paid  in  the  first  instance  by  the 
town  or  county  and  the  state  afterward   " rewards"   them, 


270  THE  ART  OF  ROADMAKING 

paying  its  share  if  the  road  is  finished  according  to  specifica- 
tions. The  rewards  vary  from  $250  to  $1000  per 
Michigan.  m^  depending  on  the  kind  of  road  built.  No 
part  of  the  cost  is  assessed  upon  the  abutting  property  and  no 
aid  is  given  for  the  building  of  bridges. 

The  town  pays  for  the  cost  of  the  roads  in  the  first  instance 
on  the  order  of  the  state  highway  commissioner,  and  the  state 
then  pays  to  the  town  its  share.  This  share  varies 
Maine.  from  two-thirds  of  the  cost,  in  poor  towns,  to  three- 
sevenths  of  the  cost  in  towns  having  a  valuation  of  over  $1,000,- 
000.  No  part  of  the  cost  is  assessed  on  abutting  property, 
and  nothing  is  said  in  the  law  about  state  aid  for  bridges. 

Rhode  The  cost  of  the  roads   is   entirely  paid  by  the 

Island.  state. 


MAINTENANCE    OF    STATE    AID    HIGHWAYS 

The  state  engineer  has  charge  of  the  maintenance  of  state 
M  d    b'll      a^   highways.     The   county   reimburses   the   state 
one-third  or  one-half  the  cost  of  maintenance  accord- 
ing to  whether  the  county  is  poor  or  rich. 

The  maintenance  of  all  roads  built  with  state  aid  is  under 
the  direct  regulation  of  the  commission.  The  commission 
is  directed  to  provide  a  system  of  patrol  of  state  high- 
Hew  York.  wavs  go  that  each  section  may  be  under  constant 
supervision.  The  state  pays  the  cost  of  the  maintenance  in  the 
first  instance,  and  each  town  in  which  a  state  aid  road  lies 
repays  $50  a  year  to  the  state  for  each  mile.  The  town  super- 
intendents of  highways  carry  out  the  work  of  maintenance 
under  the  direction  of  the  commission. 

The  county  boards  must  maintain  the  state  aid  highways 
at  county  expense.     If  they  are  not  maintained  in 
aryand.     a   manner   satisfactory   to   the   state   engineer   no 
further  state  aid  is  granted  to  the  county. 

The  state  commissioner  has  charge  of  the  main- 
irgima.       tenance  of  state  aid  highways. 

The  maintenance  of  state  aid  roads  is  in  the  hands  of  the 

highway    commission.     They   must    contract   with   towns    to 

t  maintain    the    roads    properly.     Each    town    pays 

chuastts        ^^  Per  m^e  Per  annum  f°r  maintaining  the  state 
aid  roads  and  the  remainder  is  paid  by  the  state. 
The  expense  of  snow  removal  is  borne  by  the  town  alone. 
The  maintenance  of  state  aid  highways  is  in  the  hands  of 


STATE  AID  LAWS  271 

the  state  highway  commissioner  and  the  state  pays  the  whole 
cost  at  first.     The  towns  reimburse  the  state  one- 
fourth  the  cost  of  maintaining  their  roads. 

The  towns  are  charged  with  the  maintenance  of  the  state 
aid  roads  and  pay  only  one-fourth  of  the  cost.  The  state 
pays  three-fourths  of  the  cost  and  if  the  roads  are 
not  properly  maintained  the  state  commissioner 
may  take  the  work  out  of  the  hands  of  the  town,  in 
which  case  the  town  must  pay  25  per  cent  of  the  cost  to  the  state. 

The  county  highway  engineer  is  charged  with  keeping  the 
state  aid  roads  in  good  condition,  and  the  expense  is  all  borne 
by  the  county.     If  the  roads  are  not  maintained 
in  a  manner  satisfactory  to  the  state  highway  com- 
missioner he  is  instructed  by  law  to  refuse  any  further  peti- 
tions for  state  aid  from  that  county  until  the  roads  are  re- 
paired in  an  acceptable  manner. 

The  state  aid  roads  are  maintained  at  county  expense  by  the 
supervisors   of   the   districts   through   which   they 
pass.     These  supervisors   act   under  the   direction 
of  the  state  highway  commissioner. 

State  aid  roads  must  be  maintained  by  the  coun- 
ties  at  their  own  expense. 

State  aid  roads  must  be  maintained  by  the  county  or  town 
petitioning  for  their  construction.     If  they  are  not 
properly  maintained  the  state   commissioner  does 
not  grant  any  further  state  aid  to  them. 

Towns  must  maintain  state  aid  roads  at  their  own  . 

expense  to  the  satisfaction  of  the  state  highway 
commissioner. 

The  state  maintains  all  roads  built  by  the  state          Rhode 
and  charges  none  of  the  cost  to  the  locality  except-          island6 
ing    that    the   town    must    keep    the    roads    free 
from  snow. 

CONVICT  LABOR  ON  ROADS. 

Connected  with  an  active  interest  on  the  part  of  the  state 
in  road  building  one  feature  that  always  attracts  a  great  deal 
of  attention  is  the  possibility  of  employing  the  state  convicts 
in  either  preparing  the  material  or  in  actually  constructing 
the  roads.  A  number  of  the  southern  states  have  had  very 
good  success  in  using  gangs  of  convicts  to  construct  the  state 
roads.  Almost  every  highway  commissioner  from  the  north- 


272  THE  ART  OF  ROADMAKING 

ern  states  who  has  examined  into  the  practical  operation  of 
this  system  in  the  south  has  returned  with  the  opinion  that  it 
would  not  be  readily  adaptable  to  northern  conditions.  A 
large  percentage  of  the  convicts  in  the  south  are  negroes  in 
prison  for  petty  offenses,  and  very  good  results  have  been 
obtained  in  using  gangs  of  them  in  road  work.  No  northern 
state,  in  which  the  convicts  are  almost  all  white  men,  has  ever 
attempted,  on  any  large  scale,  to  use  their  convicts  in  this 
manner. 

The  only  northern  state  that  has  used  its  convicts  to  any 
extent  in  road  construction  is  Illinois.  In  that  state  they 
have  adopted  the  plan  of  establishing  stone-crushing  plants 
at  the  two  penitentiaries.  The  stone  produced  at  these  plants 
is  given  by  the  state  without  charge  to  the  towns  or  counties 
desiring  to  use  it,  under  the  restriction  that  it  must  be  used 
according  to  the  directions  of  the  state  highway  commission. 

EXCERPTS  FROM  SPECIFICATIONS  USED  IN  CON- 
STRUCTING STATE  AID  ROADS  IN  MASSACHU- 
SETTS, NEW  JERSEY,  NEW  YORK,  CONNECTICUT, 
PENNSYLVANIA,  AND  MARYLAND.* 

MASSACHUSETTS 
EARTHWORK 

The  roadbed  shall  be  graded  for  the  width  of true  to  the  lines 

and  grades  given  by  the  engineer  and  in  conformity  with  the  plans, 
profiles,  and  cross-sections  furnished  by  the  commissioners,  and  so  shaped 
that  after  the  broken  stone  is  rolled  in  place  the  surface  of  the  roadway 
shall  have  a  crown  of  three-quarters  of  an  inch  to  the  foot. 

All  clay  and  spongy  material  shall  be  removed  to  a  depth  to  be  deter- 
mined by  the  engineer,  and  the  space  thus  made  shall  be  filled  with 
such  material  as  the  engineer  may  direct. 

In  general,  embankments  will  be  made  from  material  from  within  the 
location  of  the  road,  as  will  also  all  filling  and  grading,  but  there  if  is  not 
sufficient  suitable  material  in  the  excavation,  in  the  opinion  of  the 
engineer,  the  contractor  shall  find  such  material  outside  of  the  highway 
location.  Such  material  will  be  classed  as  borrow. 

Embankments  shall  be  formed  of  successive  layers  of  not  more  than 

*  Abstracted  from  Office  of  Public  Roads  Bulletin  No.  29,  June,  1907. 


STATE  AID  LAWS  273 

twelve  (12)  inches  in  thickness,  each  layer  to  be  thoroughly  rolled  by  a 
roller  weighing  not  less  than  two  tons. 

All  trees,  stumps,  and  roots  within  the  roadbed  and  on  slopes  shall  be 
grubbed  up  and  removed  as  the  engineer  may  direct,  without  additional 
compensation. 

Ditches  of  such  width  and  depth  as  the  engineer  may  direct  shall  be 
excavated  by  the  contractor  wherever  the  engineer  may  order  them,  at 
the  contract  price  for  excavation. 

All  surfaces  in  slopes  or  on  embankments,  whether  old  or  new,  shall 
be  left  with  neat  and  even  surfaces  according  to  the  lines,  grades,  and 
directions  given  by  the  engineer,  without  additional  compensation. 

All  measurements  of  earthwork  shall  be  made  in  excavation. 

Material  obtained  from  excavation  within  the  limits  of  the  location  and 
used  in  embankments,  or  for  any  other  purpose,  will  be  paid  for  as 
excavation  only. 

Allowance  for  culvert  excavation  will  include  only  one  (1)  foot  outside 
of  the  masonry  sections,  as  shown  on  plans. 

BORROW 

When,  in  the  opinion  of  the  engineer,  there  is  not  sufficient  suitable 
material  within  the  limits  of  the  highway  location  of  the  section  under 
contract,  to  form  the  necessary  embankments,  or  for  subgrading,  or  for 
shoulders,  the  contractor  shall  obtain  such  material  from  outside  the 
highway  location.  This  material  shall  be  known  as  borrow,  and  may 
be  of  any  quality  satisfactory  to  the  engineer  for  the  purpose  for  which 
it  is  required. 

If  found  within  a  radius  of  one  thousand  (1000)  feet  from  any  point  on 
said  section  under  contract  it  will  be  paid  for  at  the  borrow  price. 

If,  however,  in  the  opinion  of  the  engineer,  no  suitable  material  can  be 
obtained  within  the  limit  just  described,  the  contractor  shall  find  satis- 
factory material  at  a  greater  distance.  In  this  event,  in  addition  to  the 
regular  borrow  price,  the  sum  of  one-half  (£)  cent  per  cubic  yard  for  each 
one  hundred  (100)  feet  of  overhaul  shall  be  allowed  him  for  all  material 
so  supplied,  the  length  of  haul  to  be  measured  from  the  pit  along  the 
shortest  available  route  to  the  one  thousand  (1000)  foot  limit  above 
described. 

Borrow  pits  will  be  cross-sectioned  and  all  quantities  will  be  measured 
in  the  pits. 

LEDGE  EXCAVATION 

Only  such  ledge  as  requires  blasting  for  its  removal,  and  boulders  of 
one-half  (£)  a  cubic  yard  or  more  in  volume,  will  be  estimated  as  ledge 
excavation. 

No  allowance  for  ledge  excavation  in  the  roadbed  shall  be  made  outside 
of  or  for  more  than  twelve  (12)  inches  below  the  lines  indicated  on  the 


274  THE  ART  OF  ROADMAKING 

cross-sections  showing  the  finished   surface,  the  side  slopes  to  be  one- 
fourth  (i)  to  one  (1). 

Allowance  for  ledge  in  drains  will  be  made  on  the  basis  of  a  width  of 
trench  of  two  (2)  feet  and  a  depth  of  four  (4)  inches  below  the  invert  of 
the  pipe;  allowance  for  ledge  in  gutters  will  be  made  on  the  basis 
of  the  width  of  the  gutter  and  (12)  inches  in  depth  below  the  proposed 
surface. 

CULVERTS 

Reinforced  Portland  cement-concrete  culverts  shall  be  constructed 
where  ordered  by  the  engineer  to  the  lines  and  grades  given  by  him. 

Culvert  ends  shall  be  laid  parallel  to  the  center  line  of  the  roadway. 
All  culvert  masonry  shall  be  measured  in  accordance  with  the  dimen- 
sions shown  on  the  plans. 

No  allowance  shall  be  made  for  cofferdams,  pumps,  labor,  etc.,  which 
may  be  necessary  on  account  of  water. 

PORTLAND  CEMENT  CONCRETE  MASONKY 

The  concrete  shall  be  composed  of  broken  stone  or  screened  gravel, 
and  sand — all  of  which  shall  be  clean,  hard,  durable,  sharp,  and  free 
from  clay,  dirt,  and  other  objectionable  material — Portland  cement  and 
fresh,  clean  water. 

To  each  part  of  Portland  cement  there  shall  be  by  volume  two  (2) 
parts  of  sand  and  five  (5)  parts  of  broken  stone  or  srceened  gravel,  and 
such  a  proportion  of  water  as  the  engineer  may  from  time  to  time  deter- 
mine. 

The  broken  stones  or  gravel  stones  shall  be  of  the  following  sizes: 

For  all  work  less  than  six  (6)  inches  in  thickness  the  stones  may  vary 
in  their  longest  dimension  from  one-quarter  (£)  of  an  inch  to  three- 
quarters  (|)  of  an  inch;  between  six  (6)  inches  and  twelve  (12)  inches, 
from  one-quarter  (£)  of  an  inch  to  one  and  one-quarter  (1J)  inches;  more 
than  twelve  (12)  inches  in  thickness,  from  one-quarter  (j)  inch  to  two 
and  one-half  (2^)  inches. 

The  cement  and  sand  shall  first  be  thoroughly  mixed  dry,  in  the 
proportions  specified,  in  proper  boxes.  Clean  water  shall  then  be  added 
and  the  materials  thoroughly  mixed.  The  broken  stone,  previously 
drenched  with  water,  shall  then  be  deposited  in  this  mixture  and  the 
ingredients  thoroughly  mingled  and  turned  over  until  each  stone  is 
covered  with  mortar.  The  batch  shall  then  be  carefully  deposited  without 
delay  and  thoroughly  rammed  in  layers  not  more  than  six  (6)  inches 
in  depth  until  the  water  flushes  to  the  surface  and  all  the  voids  are  filled. 

The  concrete  shall  not  be  allowed  to  fall  from  any  considerable  height. 

Before  the  concrete  is  placed  in  the  moulds,  a  sheet-iron  plate,  six  or 
eight  inches  in  width  and  about  six  feet  long,  or  of  such  other  dimensions 
as  the  contractor  may  find  convenient,  shall  be  held  in  position  one  and 


STATE  AID  LAWS  275 

one-half  (1£)  inches  from  the  surface  of  the  mould  or  form.  The  space 
between  the  form  and  this  separator  shall  be  filled  with  mortar,  composed 
of  one  part  of  Portland  cement  and  one  part  of  sand,  mixed  to  such  a 
consistency  as  the  engineer  may  direct,  and,  if  he  shall  so  direct,  the 
mortar  shall  be  thoroughly  spaded  after  it  is  placed.  Only  a  small 
batch  shall  be  mixed  at  a  time,  and  then  only  as  needed.  Immediately 
after  the  space  between  the  separator  and  the  form  is  filled  with  mortar 
the  ordinary  concrete  shall  be  placed  behind  the  separator,  the  separator 
removed,  and  the  backing  and  facing  thoroughly  rammed  together  to 
a  close  bond.  No  delay  shall  be  permitted  in  placing  the  concrete 
backing,  and  both  the  facing  and  the  backing  shall  be  done  as  nearly 
simultaneously  as  is  possible. 

Should  voids  be  discovered  when  the  forms  are  taken  down,  the 
defective  work  is  to  be  removed  and  the  space  refilled  with  one  to  one 
cement  mortar.  The  exposed  surfaces  shall  be  smoothed  over  with  a 
neat  Portland  cement  grout,  laid  on  with  a  brush,  until  a  smooth  surface 
is  secured. 

Centers  and  forms,  satisfactory  to  the  engineer,  shall  be  provided  by 
the  contractor.  They  shall  be  made  of  planed  lumber  and  shall  fit  the 
curves  and  shapes  of  the  work.  The  sheathing  shall  be  laid  tight  and 
shall  be  made  clean  before  using. 

The  centers  shall  be  true  to  the  lines,  satisfactorily  supported  and 
firmly  secured,  and  shall  remain  in  place  as  long  as  the  engineer  may 
direct,  and  shall  be  replaced  by  new  ones  when  they  lose  their  proper 
dimensions  or  shape. 

In  connecting  concrete  already  set  with  new  concrete,  the  surface  shall 
be  cleaned  and  roughened  and  mopped  with  a  mortar  composed  of  one 
part  Portland  cement  and  one  part  sand. 

When  work  is  done  under  such  conditions  that  the  mortar  is  liable  to 
freeze,  the  contractor  shall  provide  the  necessary  means  for  and  shall 
thoroughly  heat  all  materials,  and  also  the  water,  and  shall  thoroughly 
protect  the  masonry  from  damage  by  rain  and  frost  during  and  after 
laying. 

During  warm  and  dry  weather,  and  whenever  the  engineer  may  direct 
all  newly  built  concrete  shall  be  kept  well  shaded  from  the  sun  and  well 
sprinkled  with  water  until  set. 

In  laying  concrete  under  water  the  concrete  shall  not  fall  from  any 
considerable  height,  but  be  deposited  in  the  allotted  place  in  a  compact 
mass.  The  concrete  must  not  be  rammed,  but  leveled  with  a  rake  or 
other  suitable  tool  immediately  after  being  deposited.  No  concrete  shall 
be  laid  in  running  water. 

Expanded  metal  or  twisted  rods,  to  be  furnished  to  the  contractor  by 
the  commission,  shall  be  imbedded  in  the  concrete  by  the  contractor  as 
directed  by  the  engineer,  without  extra  compensation. 

No  back-filling  or  loading  whatever  shall  be  placed  on  or  against  the 
concrete  masonry  until  ordered  by  the  engineer. 


276  THE  ART  OF  ROADMAKING 

The  Massachusetts  highway  commission  will  furnish  all  cement  to  be 
used  in  this  work  and  will  deliver  it  to  the  contractor  at  the  nearest 
railroad  freight  station.  The  contractor  shall,  at  his  own  expense,  team 
the  cement  to  the  work  and  store  it,  and  protect  it  from  the  weather  to 
the  satisfaction  of  the  engineer. 

The  price  to  be  paid  per  cubic  yard  for  concrete  masonry  shall  include 
the  back-filling  and  all  necessary  centers  and  forms,  and  all  work  on  the 
same,  and  no  allowance  shall  be  made  for  cofferdams,  pumping  or  bailing, 
or  for  any  materials  or  labor  necessary  on  account  of  water. 

All  concrete  shall  be  measured  in  accordance  with  the  dimensions 
shown  on  plans. 

SHAPING  SURFACE  FOR  BROKEN  STONE 

Before  the  broken  stone  is  spread  the  roadbed  shall  be  shaped  to  a 
true  surface,  conforming  to  the  proposed  cross-section  of  the  highway 
and  rolled  by  a  steam  roller,  unless  otherwise  ordered  by  the  engineer. 
All  depressions  occurring  must  be  filled  with  suitable  material  and  again 
rolled,  until  the  surface  is  smooth  and  hard,  the  width  to  be  paid  for 
to  include  only  the  width  of  broken  stone. 


BROKEN  STONE 

Broken  stone,  consisting  of  -  — ,  shall  be  spread  and  rolled  on  the 
roadbed  prepared  as  hereinbefore  described,  as  follows: 

The  width  of  the  broken  stone  shall  be  —       -  ( — )  feet. 

All  broken  stone  used  shall  be  laid  in  layers  or  courses.  The  bottom 
course  shall  consist  of  stones  from  one  and  one-quarter  (1^)  inches  to 
two  and  one-half  (2^)  inches  in  their  longest  dimension ;  the  upper  course 
of  stone  from  one-half  (^)  inch  to  one  and  one-quarter  (lj)  inches  in 
their  longest  dimension. 

The  bottom  course  shall  be  —  —  ( — )  inches  deep  at  the  center  and 
-  ( — )  inches  deep  at  the  sides  after  rolling.  The  top  course  shall 

be —  ( — )  inches  deep  at  the  center  and  —  —  (— )  inches  deep  at 

the  sides  after  rolling. 

After  the  two  courses  above  described  are  thoroughly  compacted, 
broken-stone  screening  shall  be  laid  on,  watered,  and  rolled  until  the 
mud  flushes  to  the  surface.  The  screenings  so  used  shall  not  be  larger 
than  will  pass  through  a  half-inch  mesh  and  shall  contain  all  the  dust. 
Care  must  be  taken  to  lay  on  only  enough  of  the  screenings  to  cover  the 
larger  stones. 

Each  course,  bottom,  top,  and  binder  shall  be  rolled  separately  by  a 
steam  roller  and  evened  up  with  material  of  the  same  size  and  quality  as 
has  been  used  in  that  particular  course,  and  to  the  satisfaction  of  the 
engineer. 


STATE  AID  LAWS  277 

All  broken  stone  shall  be  spread  from  the  carts  by  hand,  or  from  a 
dumping  board,  of  from  self-spreading  carts. 

No  soft  or  disintegrated  stone  shall  be  used. 

If  so  ordered  by  the  engineer  the  thickness  of  the  broken  stone  shall 
be  increased  or  diminished  at  such  points  as  he  may  direct. 

The  grade  of  the  finished  surface  of  the  road  shall  present  a  crown  of 
three-quarters  (J)  of  an  inch  to  the  foot. 

If  local  stone  or  stone  not  shipped  by  rail  is  used,  it  shall  be  weighed 
on  scales  furnished  by  and  at  the  expense  of  the  contractor.  Said  scales 
shall  be  satisfactory  to  the  engineer  and  they  shall  be  sealed  at  the 
expense  of  the  contractor  as  often  as  the  engineer  may  deem  necessary 
to  insure  their  accuracy. 

A  sworn  weigher,  to  be  appointed  and  compensated  by  the  Massa- 
chusetts highway  commission,  shall  weigh  all  broken  stone  required  to- 
be  weighed  as  above  provided. 

If  the  stone  is  shipped  by  rail  the  car  weights  will  be  accepted. 


VITRIFIED  CLAY  PIPE  AND  IRON  WATER  PIPE  (FOR  CULVERTS) 

Vitrified  clay  pipe  and  iron  water  pipe  shall  be  furnished  and  laid 
where  directed  by  the  engineer. 

All  clay  pipe  shall  be  of  first  quality,  salt  glazed,  free  from  blisters- 
and  cracks,  straight  and  round.  If  eighteen  (18)  inches  or  more  in 
diameter  the  pipe  shall  be  "double  strength,"  or  if  ordered  by  the 
engineer,  ordinary  pipe  may  be  used  and  laid  in  concrete,  which  shall 
be  tamped  about  the  pipe  to  the  satisfaction  of  the  engineer.  If,  how- 
ever, concrete  is  used  it  shall  be  paid  for  at  the  regular  price  for  con- 
crete. 

All  iron  pipe  shall  be  of  the  best  quality  of  water  pipe  and  free  from 
imperfections  of  any  kind. 

All  pipe  shall  be  laid  true  to  the  lines  and  grades  furnished  by  the 
engineer.  Nothing  but  selected  fine  material,  free  from  large  stones, 
shall  be  placed  around  and  under  the  pipe,  and  all  material  placed  under 
and  about  the  pipe  shall  be  thoroughly  tamped  in  place  by  a  thin  iron 
tamping  bar.  All  joints  shall  be  made  of  first  quality  natural  cement 
mortar,  mixed  in  proportion  of  one  (1)  part  cement  to  one  (1)  part  of 
clean,  sharp  sand,  carefully  filled  in  all  around  the  pipe.  The  ends  of 
pipe  drains  used  as  culverts  must  be  protected  by  concrete  masonry  or 
concrete  walls.  The  price  per  foot  paid  for  pipe  laid  as  above  includes 
the  cost  of  trenching  and  back-filling,  and  all  incidental  work  except 
the  masonry  ends;  provided,  however,  that  when  the  depth  of  the  trench 
exceeds  five  (5)  feet  all  excavation  necessary  on  account  of  additional 
depth  shall  be  paid  for  by  the  cubic  yard  at  the  regular  contract  price 
for  excavation. 


278  THE  ART  OF  ROADMAKING 


GUARD  RAIL 

Fencing  shall  be  placed  on  edges  of  embankments  and  at  such  other 
places  along  the  road  as  the  engineer  may  deem  necessary.  It  shall  be 
of  the  section  shown  on  plan;  the  posts  shall  be  of  well-seasoned,  straight, 
sound  chestnut  or  cedar,  not  less  than  six  (6)  inches  in  diameter,  spaced 
eight  (8)  feet  apart  on  centers,  the  bottom  of  each  post  to  be  sawed  off 
square  and  set  plumb  in  straight  lines,  three  (3)  feet  into  the  ground 
and  three  and  one-half  (3V)  feet  above  the  ground,  and  the  back-filling 
thoroughly  tamped.  All  bark  shall  be  removed  before  setting,  all  knots 
hewn  down  to  face  and  the  exposed  surfaces  shaved.  The  top  rails  shall 
be  four  (4)  inches  square  and  the  side  rails  of  two  by  six  (2X6)  inch 
well-seasoned,  straight-grained  spruce,  or  other  wood  satisfactory  to  the 
engineer,  planed,  free  from  loose  or  unsound  knots,  and  both  top  and 
side  rail  shall  be  notched  into  and  securely  fastened  to  the  posts,  as 
shown  in  the  plan,  and  be  long  enough  to  extend  over  three  (3)  posts 
and  break  joints. 

All  parts  of  the  exposed  surface  of  the  fence  shall  be  painted  with  one 
coat  of  white  lead  and  linseed  oil. 

At  culverts  square  iron  posts,  one  and  one-quarter  (1|)  inches  square, 
shall  be  used,  set  into  the  coping  stone  at  least  four  (4)  inches,  and  leaded. 
The  side  rail  shall  be  bolted  to  the  iron  posts  with  two  bolts  set  in  holes 
drilled  through  each  post. 

SIDE  DRAINS 

Drains  will  be  built  where  directed  by  the  engineer. 

All  drains  must  be  carried  to  an  outlet  approved  by  the  engineer. 

The  drain  trench  shall  be  excavated  to  a  width  of  twelve  (12)  inches 
at  the  bottom  and  fifteen  (15)  inches  at  the  top,  and  shall  be  excavated 
only  as  fast  as  the  drain  can  be  finished. 

When  the  grade  of  the  finished  road  is  three  (3)  inches  or  more  to  the 
hundred  (100)  feet,  the  bottom  of  the  drain  trench  must  be  three  and 
one-half  (3£)  feet  below  the  finished  surface  of  the  road  at  that  part  of 
the  cross-section. 

On  the  bottom  of  this  trench  shall  be  placed  two  (2)  inches  of  gravel 
or  broken  stone  which  will  pass  through  a  one  and  one-quarter  (1^) 
inch  mesh,  and  not  through  a  half  (£)  inch  mesh. 

On  this  material  shall  be  laid  a  five  (5)  inch  salt-glazed  vitrified  clay 
pipe,  with  bell  and  spigot  joints,  unless  otherwise  ordered,  with  open 
joints,  and  the  bell  ends  toward  the  rising  grade. 

All  pipe  must  be  laid  true  to  a  line  and  grade,  and  no  pipe  is  to  be  laid 
on  a  grade  of  less  than  three  (3)  inches  in  one  hundred  (100)  feet. 

Gravel  or  broken  stone  of  the  sizes  already  described  shall  be  filled 
about  the  pipe  and  over  it  for  a  depth  of  one  (1)  foot.  This  must  be 
carefully  tamped  about  and  rammed  over  the  pipe.  The  remainder  of 


STATE  AID  LAWS  279 

the  trench  is  to  be  filled  with  stone  which  will  pass  through  a  three  (3) 
inch  and  not  through  a  one  (1)  inch  mesh,  and  this  material  shall  be 
thoroughly  tamped.  Any  sand,  silt,  or  earth  getting  into  the  pipe  or 
the  interstices  of  the  stone  in  the  trench  must  be  removed  by  the  con- 
tractor at  his  own  cost,  even  if  it  be  necessary  to  rebuild  the  drain. 

Where,  in  the  opinion  of  the  engineer,  it  is  necessary  to  extend  a  drain 
to  an  outlet  beyond  the  section  needing  to  be  drained,  the  pipe  will  be 
laid  with  cement  joints,  true  to  line  and  grade,  and  the  gravel  or  stone 
in  the  trench  omitted,  the  trench  being  back-filled  with  the  material 
excavated  from  the  same. 

Where  a  pipe  is  carried  through  a  bank  the  outlet  must  be  protected 
by  masonry,  as  provided  in  pipe  culverts. 

The  price  per  lineal  foot  includes  the  cost  of  trenching  and  refilling 
with  gravel  or  broken  stone,  the  cost  of  the  pipe  and  laying,  as  well  as 
all  incidental  work. 

No  allowance  will  be  made  for  pipe  larger  than  above  specified  laid  in 
any  drain  unless  the  larger  pipe  has  been  ordered  in  writing  by  the 
engineer. 

STONE  FILLING 

At  such  places  as  the  engineer  may  direct,  stone  filling  shall  be  placed. 
Excavations  shall  be  made  to  the  lines  shown  on  the  cross-sections.  The 
stones  may  be  either  wall  stones  or  cobbles  ranging  in  size  from  the 
smallest  obtainable  to  those  not  exceeding  eight  (8)  inches  in  their 
longest  dimension,  and  the  larger  stones  shall  be  placed  at  the  bottom. 

The  excavation  will  be  paid  for  at  the  regular  price  for  excavation. 

The  stone  filling  will  be  measured  according  to  the  original  cross- 
sections,  without  allowance  for  shrinkage  or  settlement,  and  paid  for 
by  the  cubic  yard. 

CATCH  BASINS 

Catch  basins  will  be  built  of  brick  masonry  or  Portland  cement  concrete, 
as  shown  on  plan  and  in  accordance  with  the  directions  of  the  engineer. 

All  bricks  used  shall  be  well  formed  and  hard  burnt  and  shall  be  well 
soaked  in  water  before  laying. 

The  joints  shall  be  thoroughly  flushed  full  of  mortar,  consisting  of  one 
part  of  natural  cement  of  the  best  quality  and  two  parts  of  coarse,  clean, 
sharp  sand,  free  from  loam  and  pebbles. 

No  joint  on  the  face  shall  be  greater  than  one-quarter  inch. 

After  the  bricks  are  laid  the  joints  shall  be  neatly  pointed  on  the  inside. 

As  the  walls  are  laid  up  they  shall  be  well  plastered  with  mortar  on 
the  outside. 

The  contractor  is  to  furnish  all  labor,  tools,  and  materials  necessary 
for  the  basins,  excepting  the  frames  and  grates,  which  will  be  furnished 


280  THE  ART  OF  ROADMAKING 

by  the  commission,  and  delivered  at  the  railroad  freight  station  nearest 
to  the  site  of  the  work.  The  price  paid  for  each  basin  will  include  all  ex- 
cavation, back-filling,  and  incidental  work. 

COBBLE-STONE  GUTTERS 

Paved  gutters  will  be  built  where  directed  by  the  engineer,  the  same  to 
be  laid  by  journeymen  pavers. 

No  gutter  is  to  be  laid  until  after  the  broken  stone  has  been  rolled,  unless 
otherwise  ordered  by  the  engineer. 

In  no  case  is  the  roller  to  pass  over  any  part  of  any  paved  gutter. 

Gutters  not  exceeding  four  hundred  (400)  feet  in  length  shall  be  three  (3) 
feet  wide  with  a  shoulder  one  (1)  foot  wide  and  a  dish  of  three  (3)  inches. 

Gutters  exceeding  four  hundred  (400)  feet  in  length  shall  increase  the 
dish  above  this  length  at  the  rate  of  one  (1)  inch  to  each  three  hundred 
(300)  feet. 

All  stone  used  in  gutters  shall  be  rounded  field,  bank,  or  river  stone; 
no  flat,  shaky,  or  rotten  stone  shall  be  used . 

The  stone  may,  on  the  average,  lay  from  four  (4)  to  six  (6)  square 
yards  to  the  ton.  A  cubic  yard  may  be  estimated  to  weigh  one  and  one- 
third  (1£)  tons. 

The  larger  selected  stone  will  be  laid  in  the  gutter  row  and  on  the  edges 
to  a  true  line  and  grade,  with  the  largest  diameters  lengthwise  of  the  road. 
All  other  stone  will  be  laid  with  the  longest  diameters  across  the  gutter. 

The  trench  shall  be  excavated  to  a  depth  of  twelve  (12)  inches  below  the 
finished  grade  of  the  gutter;  gravel  shall  then  be  spread  and  rammed 
to  a  depth  of  four  (4)  inches.  A  layer  of  bedding  sand,  or  gravel  free 
from  stone  larger  than  one-half  ($)  inch  in  diameter,  shall  then  be  spread 
of  a  sufficient  thickness  to  bring  the  gutter  stone  which  are  bedded  in  it 
to  the  proper  grade  and  cross-section  after  they  are  thoroughly  rammed. 

Each  stone  is  to  be  rammed  to  an  unyielding  foundation.  The  con- 
tractor shall  employ  one  rammer  to  every  two  pavers.  The  surface 
shall  then  be  covered  with  coarse  sand  or  fine  screened  gravel  free  from 
clay  or  dirt,  which  must  be  well  broomed  into  all  joints.  The  stone  shall 
then  be  rerammed  and  the  surface  left  smooth  and  even.  If  from  any 
cause  the  stone  in  a  gutter  shall  have  been  disturbed  and  left  uneven, 
they  must  be  relaid  by  the  contractor  and  at  his  cost.  Sand  or  screened 
gravel  shall  then  be  spread  over  the  entire  surface  of  sufficient  depth 
to  fill  all  interstices. 

The  edge  of  the  gutter  toward  the  road  shall  be  left  one-quarter  (£) 
inch  below  the  surface  of  the  adjoining  broken  stone;  in  no  case  must  it 
project  above  it. 

All  broken  stone  which  may  be  disturbed  during  the  paving  of  the 
gutter  must  be  carefully  replaced  and  thoroughly  rammed. 

The  bank  on  the  outside  of  the  gutter  must  be  sloped  to  the  gutter,  so 
as  to  have  no  bunches  or  depressions  on  its  surface. 


STATE  AID  LAWS  281 

NEW  JERSEY 

SUBFOUNDATIONS 

When  the  excavations  and  embankments  have  been  brought  to  a  proper 
depth  below  the  intended  surface  of  the  roadway,  the  cross-section  thereof 
conforming  in  every  respect  to  the  cross-section  of  the  road  when  finished, 
the  same  shall  be  rolled  with  a  —  —  ton  roller  until  it  is  —  —  inches 
below  the  intended  surface  of  the  road  and  is  approved  by  the  engineer 
and  supervisor.  If  any  depressions  form  under  such  rolling,  owing  to 
improper  material  or  vegetable  matter,  the  same  shall  be  removed  and 
good  earth  substituted,  and  the  whole  rerolled  until  thoroughly  solid 
and  to  above-mentioned  grade.  Water  must  be  applied  in  advance  of 
the  roller  when,  in  the  opinion  of  the  engineer  and  supervisor,  it  is 
necessary. 

STONE  CONSTRUCTION 
TELFORD  FOUNDATIONS 

After  the  roadbed  has  been  formed  and  rolled,  as  above  specified, 
and  has  passed  the  inspection  of  the  engineer  and  supervisor,  a  bottom 
course  of  stone,  of  an  average  depth  of  —  —  inches,  is  to  be  set  by  hand 
as  a  close,  firm  pavement,  the  stones  to  be  placed  on  their  broadest  edges 
lengthwise  across  the  road  in  such  manner  as  to  break  joints  as  much  as 
possible,  the  breadth  of  the  upper  edge  not  to  exceed  four  (4)  inches. 
The  interstices  are  then  to  be  filled  with  stone  chips,  firmly  wedged  by 
hand  with  a  hammer,  and  projecting  points  broken  off.  No  stone  of 
greater  length  than  ten  (10)  inches  or  width  of  four  (4)  inches  shall  be 
used,  except  each  alternate  stone  on  outer  edge,  which  shall  be  double 
the  length  of  the  others  and  well  tied  into  the  bed  of  the  road.  All 
stones  with  a  flat,  smooth  surface  must  be  broken.  The  whole  surface 
of  this  pavement  must  be  subjected  to  a  thorough  settling  or  ramming 
with  heavy  sledgehammers,  and  thoroughly  rolled  with  a  —  —  ton  — 
roller.  No  stone  larger  than  two  and  one-half  (2^)  inches  shall  be  left 
loose  on  top  of  telford. 

MACADAM 
FIRST  COURSE  OF  BROKEN  STONE 

After  the  roadbed  has  been  formed  and  rolled,  as  above  specified, 
and  has  passed  the  inspection  of  the  engineer  and  supervisor,  the  first 
layer  of  broken  stone,  consisting  of  two  and  one-half  (2J)  inch  stone, 
or  stone  that  will  pass  through  a  ring  three  (3)  inches  in  diameter,  shall 
be  deposited  in  a  uniform  layer,  having  a  depth  of  —  —  inches,  and  rolled 
repeatedly  with  a  —  —  ton  —  —  roller  until  compacted  to  the  satisfac- 
tion of  the  engineer  and  supervisor.  No  stone  in  this  course  shall  be  less 
than  two  (2)  inches  in  length. 


282  THE  ART  OF  ROADMAKING 

The  depth  of  loose  stone  in  this  and  all  other  courses  must  be  measure! 
by  blocks  the  required  thickness  of  the  said  loose  stone.  These  blocks 
must  be  placed  at  frequent  intervals  amid  the  loose  stone  when  being 
spread . 

BINDER  BETWEEN  FIRST  AND  SECOND  COURSE  FOR  TELFORD  OR  MACADAM. 

On  the  first  course  of  stone  a  quantity  of  —  —  binder  shall  be  spread 
in  a  uniform  layer,  and  the  whole  rolled  until  the  stones  cease  to  sink 
or  creep  in  front  of  the  roller.  The  quantity  and  quality  of  this  and  all 
other  binding  shall  be  subject  to  the  approval  of  the  engineer  and  super- 
visor. Water  must  be  applied  in  advance  of  the  roller,  if  ordered  by  the 
engineer  or  supervisor. 

SECOND  COURSE  OF  BROKEN  STONE  FOR  MACADAM  OR  TELFORD 

The  second  course  of  broken  stone  shall  consist  of  one  and  one-naif 
(140  inch  stone;  that  is,  every  piece  of  stone  shall  be  broken  so  that  it 
can  be  passed  through  a  ring  two  (2)  inches  in  diameter,  and  no  stone 
shall  be  more  than  two  (2)  inches  or  less  than  one  (1)  inch  long.  This 
course  shall  be  spread  in  a  uniform  layer  —  —  inches  in  depth  and  rolled 
until  thoroughly  settled  into  place  to  the  satisfaction  of  the  engineer  and 
supervisor.  Water  must  be  applied  as  ordered  by  the  engineer  or  super- 
visor. 

BINDER  ON  SECOND  COURSE  OF  STONE 

Binder  on  this  course  of  stone  must  be  applied  in  the  same  manner  as 
binder  on  first  course  of  stone,  as  directed  by  engineer  and  supervisor. 

SURFACE 

When  the  two  courses  are  rolled  to  the  satisfaction  of  the  engineer  and 
supervisor,  a  coat  of  fifty  (50)  per  cent  of  three-quarters  (f)  inch  stone 
and  fifty  (50)  per  cent  of  screenings,  properly  mixed,  is  to  be  spread  of 
sufficient  thickness  to  make  a  smooth  and  uniform  surface  to  the  road, 
then  again  rolled  until  the  road  becomes  thoroughly  consolidated,  hard 
and  smooth. 

Rolling  must  be  done  by  the  contractor  with  a  —  —  ton roller, 

approved  by  the  engineer. 

Any  depressions  formed  during  the  rolling,  or  from  any  other  cause, 
are  to  be  filled  with  one  and  one-half  (1£)  inch  stone,  or  three-quarter 
($)  inch  stone,  or  both,  and  screenings,  approved  by  the  engineer,  and  the 
roadway  brought  to  the  proper  grade  and  curvature  as  determined  by 
him. 

Water  must  be  applied  in  such  quantities  and  in  such  manner  as  di- 
rected by  the  engineer  or  supervisor. 


STATE  AID  LAWS  283 


MANNER  OF  ROLLING 

In  the  rolling  the  roller  must  start  from  the  side  lines  of  the  stone  bed 
and  work  toward  the  center,  unless  otherwise  directed.  The  rolling 
shall  at  all  times  be  subject  to  the  directions  of  the  engineer  and  super- 
visor, who  may,  from  time  to  time,  direct  such  methods  of  procedure  as 
in  their  opinion  the  necessities  of  the  case  may  require. 

QUALITY  OF  MATERIAL 

All  stone  must  be  as  nearly  cubical  as  possible,  broken  with  the  most 
approved  modern  stone-crushing  machinery,  free  from  all  screenings, 
earth,  and  other  objectionable  substances,  of  uniform  size,  and  the  same 
kind  and  quality,  or  as  good  in  every  particular,  as  that  shown  in  the 
engineer's  office.  The  one  and  one-half  (1£)  inch  stone,  three-quarter 
(I)  ij.ch  and  screenings  for  binder  and  final  finish  must  be  of  the  best 
trap  rock,  free  from  loam  or  clay. 

The  contractor  must  furnish  samples  to  the  engineer  of  the  kind  of  stone 
to  be  used  in  the  work  before  the  opening  of  the  bids,  and  to  the  state 
commissioner  of  public  roads  before  the  approval  of  the  contract  by  him. 

ENTRANCES  TO  DWELLINGS 

All  driveways  leading  to  dwellings  along  the  road  shall  be  macadamized 
with  the  second  course  and  finished  in  the  same  manner  as  prescribed  for 
the  main  road.  The  macadamizing  shall  be  carried  to  a  distance  of  not 
more  than  six  feet  beyond  the  gutter  line  of  the  road,  as  indicated  by  the 
engineer's  stakes,  but  in  no  case  shall  the  macadamizing  be  carried  beyond 
the  side  line  of  the  road  as  indicated  by  the  fences. 

SHOULDERING 

A  shoulder  of  firm  earth  or  gravel  is  to  be  left  or  made  on  each  side, 
extending  at  the  same  grade  and  curvature  of  road  to  side  ditches  or 
gutters.  This  shoulder  is  to  be  rolled  according  to  the  directions  of  the 
engineer. 

NEW  YORK 
ROLLING  SUBGRADE 

After  the  surface  of  the  subgrade  has  been  properly  shaped,  and  before 
any  broken  stone  or  other  material  is  put  on,  it  shall  be  thoroughly  rolled 
and  compacted.  This  rolling  shall  be  done  with  a  steam  road  roller 
weighing  approximately  ten  tons,  and  so  built  that  its  wheels  shall  cover 
when  rolling  the  entire  width  of  its  track.  The  roller  must  be  of  a  kind 
approved  by  the  state  engineer.  All  hollows  and  depressions  which 


284  THE  ART  OF  ROADMAKING 

develop  during  the  rolling  shall  be  filled  with  material  acceptable  to  the 
engineer  and  the  subgrade  shall  again  be  rolled.  This  process  of  filling 
and  rolling  shall  be  repeated  until  no  depressions  develop.  The  shoulders 
also  shall  be  rolled  in  the  same  manner,  but  in  places  where  the  character 
of  the  material  makes  the  use  of  a  ten-ton  roller  impracticable  a  lighter 
roller  shall  be  used. 

In  places  where  the  material  of  the  subgrade  or  of  the  shoulders  is 
unstable,  and  will  not  consolidate  under  the  action  of  the  roller,  and  is  so 
great  in  extent  that  its  removal  is  impracticable,  it  shall  be  formed  to  the 
desired  shape  and  treated  in  such  manner  as  may  be  necessary  to  con- 
solidate and  compact  it,  and  to  give  the  best  results  in  providing  a  stable 
foundation  for  the  entire  roadway. 

The  expense  of  all  such  special  work  shall  be  borne  by  the  contractor 
and  must  be  considered  by  him  in  making  his  proposal. 

The  bottom  course  shall  not  be  placed  on  any  subgrade  until  the  sub- 
grade  has  been  accepted  by  the  engineer. 

SURFACE  OF  ROADWAY 

The  surface  of  the  roadway  shall  be  formed  of  broken  stone  macadam 
or  any  other  material  shown  on  the  plans  or  ordered  by  the  state  engi- 
neer. When  formed  of  broken  stone  macadam  it  shall  have  the  thick- 
ness shown  on  the  plans.  In  general  it  will  be  formed  of  three  courses — 
a  bottom  course  three  inches  thick  after  being  rolled,  a  middle  course 
two  or  three  inches  thick  after  being  rolled,  and  a  top  course  one 
inch  thick  after  being  rolled. 

BROKEN  STONE  MACADAM 

Where  shown  on  plans,  called  for  in  the  specifications,  or  ordered  by 
the  state  engineer,  at  prices  named  in  the  supplementary  bidding  sheet, 
broken  stone  macadam  shall  be  placed  in  accordance  with  the  specifi- 
cations. 

BROKEN  STONE 

The  contractor  shall  submit  with  his  bid  a  written  statement  of  the 
quarries,  ledges,  or  other  sources  of  supply  from  which  he  proposes  to 
obtain  the  stone  for  the  road.  If  the  proposed  quarries  are  thoroughly 
developed  and  a  uniform  product,  satisfactory  to  the  state  engineer, 
can  be  obtained  from  them,  this  will  be  accepted  and  the  contractor 
will  be  so  informed.  If  after  trial  it  is  found  that  partially  developed 
quarries,  ledges,  or  other  sources  of  supply  do  not  furnish  a  uniform 
product,  of  if  for  any  reason  the  product  from  any  source  at  any  time 
proves  to  be  unsatisfactory  to  the  state  engineer,  he  may  decline  to 
continue  its  use  and  can  require  the  development  of  other  quarries,  or 
he  may  require  the  contractor  to  furnish  other  sources  of  supply,  and  the 


STATE  AID  LAWS  285 

contractor  shall  have  no  claim  for  increased  payment  on  account  of  such 
requirement.  Immediately  after  the  crusher  is  in  operation  the  con- 
tractor shall  furnish  to  the  engineer  in  charge  a  sample  consisting  of 
about  £  of  a  cubic  foot  of  each  size  of  the  crushed  stone  to  be  used,  showing 
character  and  size.  If  the  character  and  size  of  the  stone  submitted  are 
satisfactory  to  the  state  engineer  and  are  accepted  by  him,  the  samples 
will  be  retained  by  the  engineer,  and  all  stone  which  are  inferior  in  char- 
acter or  size  to  these  samples  will  be  rejected. 

QUALITY  OF  BROKEN  STONE 

Broken  stone  and  screenings  must  be  of  a  hard  and  compact  texture 
and  of  a  uniform  grain.  The  fragments  shall  have  rough  surfaces  such  as 
are  obtained  by  fracture.  Water-worn  pebbles  will  not  be  accepted. 
Disintegrated  and  rotten  stone  from  the  surface  of  a  quarry  or  elsewhere 
will  not  be  accepted.  All  stone  shall  be  thoroughly  clean  before  crushing 
and  must  be  well  screened  and  free  from  injurious  matter  of  every  nature. 

The  broken  stone  shall  be  spread  in  three  courses  when  the  top  course 
is  built  of  trap  rock,  granite,  gneiss,  or  any  of  the  harder  grades  of  stone; 
in  two  courses  when  the  top  course  is  built  of  limestone  or  any  of  the  softer 
grades  of  stone.  The  number  of  courses  shall  be  as  shown  on  the  plans 
or  ordered  by  the  engineer. 

BOTTOM  COURSE 

The  bottom  course,  in  either  case,  after  it  is  rolled  shall  have  the  thick- 
ness shown  on  the  plans  or  indicated  on  the  quantity  sheet,  and  may 
consist  of  approved  trap  rock,  granite,  gneiss,  or  any  of  the  harder  grades 
of  limestone  or  tough  sandstone  -  -  broken  in  fragments  that  will 
pass  through  a  three-inch  circular  ring  but  will  not  pass  through  a  two- 
inch  circular  ring. 

When  local  stone  is  crushed  to  form  the  bottom  course  only,  all  frag- 
ments that  will  pass  through  a  three-inch  circular  ring  but  will  not  pass 
through  a  one-half  inch  circular  ring  may  be  used.  Care  must  be  taken 
to  distribute  evenly  the  smaller  stone  among  the  larger  stone. 

FILLER  FOR  BOTTOM  COURSE 

The  filler  for  the  bottom  course  shall  be  either  screenings  or  sand. 
Screenings  shall  consist  of  fragments  of  the  kind  and  quality  of  stone  speci- 
fied, that  will  pass  through  a  one-half-inch  circular  ring.  They  shall  be 
free  from  any  injurious  material  and  shall  contain  all  the  dust  of  fracture. 
If  sand  is  used,  it  shall  not  be  excessively  fine  and  must  be  satisfactory 
to  the  engineer. 


286  THE  ART  OF  ROADMAKING 


MIDDLE  COURSE 

When  the  road  is  built  in  three  courses,  the  middle  course  after  it  is 
rolled  shall  have  the  required  thickness  shown  on  the  plans  or  indicated 
on  the  quantity  sheet,  and  shall  consist  of  -  -  broken  into  fragments 
that  will  pass  through  a  two-inch  circular  ring  but  will  not  pass  through 
a  one-inch  circular  ring. 

TOP  COURSE 

When  the  road  is  built  in  three  courses  the  top  course  after  it  is  rolled 
shall  have  the  required  thickness  shown  on  the  plans  or  indicated  on  the 
quantity  sheet,  and  shall  consist  of  -  -  broken  in  fragments  that  will 
pass  through  a  one-inch  circular  ring  but  will  not  pass  through  a  one- 
half  inch  circular  ring. 

When  the  road  is  built  in  two  courses  the  top  course  after  it  is  rolled 
shall  have  the  required  thickness  shown  on  the  plans  or  indicated  on 
the  quantity  sheet,  and  shall  consist  of  limestone  —  —  broken  in  frag- 
ments that  will  pass  through  a  two-inch  circular  ring  but  will  not  pass 
through  a  one-half  inch  circular  ring.  Care  must  be  taken  to  distribute 
the  smaller  stone  evenly  among  the  larger  stone. 

BINDER  FOR  MIDDLE  AND  TOP  COURSES 

Screenings  for  binder  for  middle  and  top  courses  shall  consist  of  frag- 
ments of  the  kind  and  quality  of  stone  specified,  that  will  pass  through 
a  one-half  inch  circular  ring.  They  shall  be  free  from  any  injurious 
material  and  shall  contain  all  the  dust  of  fracture. 

SPRINKLER 

The  sprinkler  shall  be  built  without  a  reach  to  allow  short  turns. 
The  tires  on  the  wheels  shall  be  at  least  six  inches  wide  and  the  axles 
shall  be  of  unequal  length,  so  that  the  front  and  rear  wheels  will  not 
roll  in  the  same  track. 

SPREADING  AND  ROLLING 

After  the  subgrade  has  been  prepared  and  has  been  accepted  by  the 
engineer,  a  layer  of  broken  stone  of  the  approved  size  and  quality  for 
bottom  course  shall  be  spread  evenly  over  it  to  such  depth  that  it  shall 
have,  when  rolled,  the  required  thickness.  The  depth  of  the  loose  stone 
shall  be  fixed  by  laying  upon  the  subgrade  cubical  blocks  of  wood  of 
the  required  size  (1^  times  thickness  of  course  to  be  formed)  and  spread- 
ing the  stone  evenly  to  the  same  thickness. 

The  roller  shall  be  run  along  the  edge  of  the  stone  backward  and  for- 
ward several  times  on  each  side  before  rolling  the  center.  Before  put- 


STATE  AID  LAWS  287 

ting  on  the  filler  the  bottom  course  shall  be  rolled  until  the  stones  do  not 
creep  or  weave  ahead  of  the  roller.  In  no  case  shall  the  screenings  or 
sand  for  filler  be  dumped  in  mass  upon  the  crushed  stone,  but  they  shall 
be  spread  uniformly  over  the  surface  from  wagons  or  from  piles  that 
have  been  placed  on  the  shoulders.  It  shall  then  be  swept  with  rattan 
or  steel  brooms  and  rolled  dry.  This  process  shall  be  continued  until 
no  more  will  go  in  dry,  when  the  surface  shall,  if  required  by  the  engi- 
neer, be  sprinkled,  to  more  effectually  fill  the  voids.  No  filler  shall  be 
left  on  the  surface. 

The  middle  course  of  stone  shall  be  spread  on  the  bottom  course  to 
such  a  depth  that  it  shall  have,  when  rolled,  the  required  thickness. 
Blocks  of  wood  (1£  times  thickness  of  course  to  be  formed)  shall  be  used 
to  fix  the  depth  of  the  loose  stone;  care  shall  be  taken  to  preserve  the 
grade  and  crown.  Before  putting  on  the  screenings  it  shall  be  rolled 
dry  until  the  stones  do  not  creep  or  weave  ahead  of  the  roller.  It  shall 
then  be  filled  with  screenings,  leaving  none  on  the  top,  and  rolled  dry. 

The  top  course  of  stone  shall  be  spread  on  the  middle  course  to  such 
a  depth  that  it  shall  have,  when  rolled,  the  required  thickness.  Blocks 
of  wood  (1£  times  thickness  of  course  to  be  formed)  shall  be  used  to  fix 
the  depth  of  the  loose  stone;  care  must  be  taken  to  preserve  the  grade 
and  crown,  also  to  prevent  a  wavy  surface.  It  shall  then  be  covered 
with  dry  screenings,  swept  and  rolled  dry,  after  which  the  road  shall 
be  sprinkled  until  saturated,  the  sprinkler  being  followed  by  the  roller. 
More  screenings  shall  be  added,  if  necessary,  and  the  sweeping,  sprink- 
ling, and  rolling  shall  continue  until  a  grout  has  been  formed  of  the 
screenings,  stone  dust,  and  water  that  shall  fill  all  the  voids  and  shall 
form  a  wave  before  the  wheels  of  the  roller.  The  road  shall  be  puddled 
as  many  times  as  may  be  necessary  to  secure  satisfactory  results. 

After  the  wave  of  grout  has  been  produced  over  the  whole  section  of 
the  road,  this  portion  of  the  road  shall  be  left  to  dry,  after  which  it  shall 
be  opened  to  travel.  Where  necessary,  enough  screenings  or  approved 
sand  shall  be  spread  on  top  of  the  macadam  to  leave  a  wearing  surface 
at  least  three-eighths  of  an  inch  thick.  This  wearing  surface  shall  be 
maintained  and  renewed,  if  necessary,  until  the  whole  road  has  been 
accepted. 

METHOD  OF  CARRYING  ON  THE  WORK 

All  work  shall  be  carried  along  together  where  practicable.  The 
stone  shall  be  rolled  and  promptly  filled  after  being  spread,  and  travel 
upon  loose  stone  shall  not  be  permitted. 

No  extra  allowance  will  be  made  for  material  driven  into  the  sub- 
grade  by  the  roller,  wagons,  or  by  other  means,  or  for  any  mistake  made 
by  the  contractor  in  preparing  subgrade.  Lighter  rollers,  rammers,  or 
other  suitable  implements  shall  be  substituted  for  the  ten-ton  steam 
roller,  if  the  engineer  so  directs. 


288  THE  ART  OF  ROADMAKING 

Before  a  road  will  be  finally  accepted  the  macadam  surface  must  be 
firm,  hard,  smooth,  regular,  well  bound,  and  must  be  covered  with  a  proper 
wearing  surface.  The  shoulders  must  be  well  formed  and  the  ditches 
clear.  The  spoil-banks,  borrow-pits,  and  all  slopes  along  the  roadsides 
must  be  left  in  regular  form.  All  waste  materials  must  be  removed 
and  the  whole  put  in  a  neat  and  workmanlike  condition. 

CONNECTICUT 
KIND  OF  STONE 
Unless  otherwise  specified,  trap  rock  will  be  required. 

COURSES  OF  STONE 

There  shall  be  two  courses  of  broken  stones  under  finishing  course; 
first  course  to  be  4  inches,  and  second  course  to  be  2  inches  over  all 
when  rolled;  no  allowance  to  be  made  for  settling. 

DIMENSIONS  OF  BROKEN  STONE 

The  stone  for  the  first  course  shall  be  from  f  of  an  inch  to  2  inches 
longest  diameter,  mixed  in  the  screens  (not  in  the  bins),  the  smaller  sizes 
to  predominate.  Stone  for  the  second  course  shall  be  from  1  inch  to 
1£  inches  longest  diameter.  No  tailings  shall  be  used  in  either  course. 

FIRST  AND  SECOND  COURSES 

The  stone  shall  be  dumped  on  the  side  of  the  road  where  it  is  possible; 
if  not,  it  can  be  dumped  on  the  side  of  the  roadbed  and  scattered  with 
shovels;  the  reason  for  this  is  that  the  stone  will  have  a  uniform  pressure 
in  rolling.  If  a  patent  spreading  wagon  is  used  by  the  contractor,  it 
will  not  be  necessary  to  dump  the  stone,  but  it  can  be  spread  by  the 
wagon.  After  stone  has  been  spread  for  the  first  course,  sufficient  to 
roll  down  to  4  inches,  a  roller  shall  be  run  over  the  stones  a  sufficient 
number  of  times  to  make  this  course  solid  and  firm,  after  which  the  second 
course  of  2  inches  shall  be  applied  in  the  same  manner  as  specified  for 
the  first  course,  and  also  receive  the  same  roller  treatment.  If  in  the 
putting  on  of  either  course  any  settling  is  found,  all  such  places  must  be 
brought  up  to  grade  level  before  any  other  course  is  commenced.  In 
the  rolling  of  these  courses  the  roller  work  must  be  continued  until  the 
broken  stone  settles  down  into  a  firm  and  compact  condition. 

FINISHING  COURSE 

This  course  shall  be  1  inch  thick  when  finished.  Trap  rock  screen- 
ings, including  dust  (no  screenings  larger  than  ^-inch  stone  will  be  al- 
lowed), shall  be  used  as  a  finishing  course.  The  screenings  (after  the 


STATE  AID  LAWS  289 

rolling  has  been  done  on  the  last  course  of  broken  stone)  shall  be  carted 
on  the  sides  of  the  road  proper  and  dumped  at  suitable  intervals,  after 
which  all  wheel  tracks  and  foot-marks  of  horses  shall  be  carefully  filled 
and  then  rolled  down  firmly.  Then  the  screenings  shall  be  scattered 
dry  over  the  surface  so.  as  to  fill  all  interstices,  and  the  roller  shall  be 
run  over  the  surface  to  shake  in  the  dust.  Immediately  after,  a  sprink- 
ling cart  shall  be  used  and  the  screenings  washed  in,  after  which  more 
screenings  must  be  added  and  sprinkled  and  rolled  again,  and  the  screen- 
ings, sprinkling,  and  rolling  must  be  continued  until  all  the  coarse  stones 
have  been  covered  and  interstices  completely  filled  and  the  road  is  firm 
and  smooth  and  will  shed  water  and  measure  in  depth  1  inch  of  screen- 
ings for  wearing  surface.  The  contractor  will  not  be  allowed  to  put 
on  the  screenings  all  at  one  time,  but  must  spread  them  on  as  described 
above,  and  will  not  be  allowed  to  deviate  from  the  above  treatment 
in  any  way.  The  contractor  must  not  wet  the  screenings  before  they 
have  been  scattered  on  the  broken  stone,  and,  furthermore,  they  must 
be  perfectly  dry  before  they  are  put  on  the  road. 


PENNSYLVANIA 
ROADBED 

The  graded  roadbed  must  be  rolled  until  firm  with  a  steam  roller 
weighing  not  less  than  16,000  pounds  nor  more  than  20,000  pounds. 
Any  depressions  formed  under  such  rolling  must  be  filled  and  rolled 
again  until  the  subgrade  presents  a  uniform  appearance  and  is  identical 
in  form  with  the  cross-section  of  the  road  when  finished.  Under  no 
circumstances  must  stone  be  laid  until  the  subgrade  has  been  thoroughly 
rolled  to  the  satisfaction  of  the  engineer  or  inspector  in  charge. 

MACADAM 

Only  good  solid  stone  shall  be  used  in  macadamizing.  Bidders  will 
name  the  kind  of  stone  they  propose  using  in  said  work,  and  also  its  lo- 
cation, unless  the  kind  of  stone  required  to  be  furnished  is  mentioned  in 
the  specifications.  On  the  prepared  roadbed  shall  be  placed  the  bottom 
course,  extending  —  —  feet  on  each  side  of  the  center  line,  and  com- 
posed of  crushed  stone  not  larger  than  will  pass  through  a  3-inch  ring 
in  all  directions  nor  smaller  than  1^-inch  size.  After  being  evenly  spread 
the  course  shall  be  thoroughly  rolled  with  the  roller  hereinbefore  specified 
until  none  of  the  stone  moves  under  the  roller.  All  material  must  be 
added  dry,  but  water  must  be  applied  ahead  of  the  roller.  The  bottom 
course  must  be inches  deep. 


290  THE  ART  OF  ROADMAKING 


TELFORD  MACADAM 

Only  good  solid  stone  shall  be  used  in  telford  construction.  Bidders 
will  name  the  kind  of  stone  they  propose  using  in  said  work,  and  also 
its  location,  unless  the  kind  of  stone  required  to  be  furnished  is  men- 
tioned in  the  specifications.  On  the  proposed  roadbed  shall  be  placed 
the  bottom  course,  extending  —  —  feet  on  each  side  of  the  center  line, 
the  stones  composing  the  course  to  be  9  to  12  inches  long  by  3  to  5  inches 
wide  and  —  —  inches  deep,  placed  vertically  by  hand  on  their  broadest 
edges.  Stones  are  to  be  laid  in  lengthwise  courses  across  the  road,  and 
all  interstices  filled  with  broken  stone  wedged  vath  a  hammer.  All 
projecting  points  must  be  broken  off  to  bring  the  surface  of  the  stone 
true  to  grade,  the  course  to  be  thoroughly  rolled  with  the  roller  here- 
inbefore specified  until  the  stone  does  not  rock  under  the  roller.  Good 
hard  native  stone  can  be  used  for  the  telford  course. 

After  completion  of  the  bottom  course,  the  second  course,  to  be  — 
inches  deep,  shall  be  applied,  of  crushed  stone  not  larger  than  will  pass 
through  a  1^-inch  ring  in  all  directions,  nor  smaller  than  f-inch  size, 
and  rolled  as  previously  directed  until  firm  and  solid,  water  being  applied 
ahead  of  the  roller. 

The  finishing  course  shall  be  1  inch  thick,  of  the  same  material  as  the 
second  course  and  composed  of  rock  screenings,  at  least  50  per  cent  of 
which  must  be  of  sizes  from  ^  inch  to  \  inch.  It  shall  be  applied  dry 
and  rolled  once  before  wetting,  then  alternate  applications  of  water  and 
rolling  until  finally  completed,  when  the  surface  must  present  a  uniform 
appearance  and  conform  to  the  shape  and  grade  fixed  by  these  specifi- 
cations and  the  accompanying  plans. 

The  several  courses  of  materials  used  in  the  construction  of  the  road 
must  each  be  of  the  required  depth  after  rolling  (allowance  for  com- 
pression should  be  at  least  one-half). 

Trap  rock  or  good  hard  blue  limestone  must  be  used  for  the  second 
and  top  courses. 

The  rolling  must  be  done  with  the  utmost  thoroughness  in  each  of 
the  courses.  In  all  rolling  the  roller  must  start  from  the  side  lines  of  the 
roadbed  and  work  toward  the  center.  The  contractor  shall  sprinkle 
and  roll  the  finished  road  every  day  for  at  least  one  week  after  the  com- 
pletion of  the  work. 

ROAD  INTERSECTIONS 

All  intersections  of  roads  are  to  be  graded  and  macadamized  in  ac- 
cordance with  the  plan,  and  in  addition  thereto  broken  stone  of  the  3- 
inch  size  must  be  spread  beyond  the  macadam  to  a  depth  of  6  inches 
for  a  distance  of  100  feet  on  the  intersecting  roads,  and  also  at  the  ends 
of  the  macadam  on  the  road  being  improved  for  at  least  100  feet;  berms 
shall  be  built  to  hold  this  stone  in  place. 


STATE  AID  LAWS 


291 


The  contractor  will  be  required  to  grade  and  put  in  a  condition  satis- 
factory to  the  state  highway  commissioner  all  existing  approaches  of 
roads  of  lanes  leading  off  the  road. 


MARYLAND 

Macadam  construction  is  to  be  used  wherever  directed  by  the  engineer 
or  provided  for  in  the  plans.  The  width  and  thickness  required  at 
different  points  is  to  be  that  designed  by  the  engineer. 

CLASSES  A,  B,  AND  C 

There  -  —  to  be  -  -  class  of  macadam  construction  to  be 
known  as  Class  A,  B,  and  C,  respectively.  -  class  shall  consist 

of  three  courses  of  broken  stone.     The  thickness  after  rolling  of  the 
various  courses  in class  is  to  be  as  follows: 


First  Course. 

Second  Course. 

Third  Course. 

Class  A  
Class  B     

4  inches  
5  inches 

2  inches  
3  inches 

(To  be  as  herein- 
after described  ) 

Class  C 

6  inches 

4  inches 

Each  course  of  broken  stone  is  to  be  applied  as  herein  specified. 


ROADBED 

MATERIAL 

The  roadbed  for  macadam  construction  is  to  consist  of  the  natural 
earth  roadbed,  prapared  and  rolled  until  firm  and  hard  in  the  following 
manner: 

If  sandy  or  other  soil  be  encountered  which  will  not  compact  readily 
under  the  roller,  a  small  amount  of  clay,  or  other  means  satisfactory 
to  the  engineer,  shall  be  used  until  a  firm,  hard  surface  is  obtained  after 
rolling. 

CUTS    AND    FILLS 

In  cuts  and  fills,  unless  otherwise  specially  directed,  the  roadbed  is 
to  be  graded  to  a  width  of  -  —  feet,  and  is  to  be  free  from  all  spongy 
and  vegetable  matter,  roots,  and  stumps.  The  portion  of  the  roadbed 
prepared  for  the  broken-stone  surface,  is  to  be  -  -  feet  wide  and 
brought  to  the  grades  and  cross-sections  as  shown  on  the  plans  and 
rolled  with  a  steam  roller  until  firm  and  hard.  All  depressions  that  may 
appear  during  the  rolling  are  to  be  filled  with  earth  and  rerolled  until  an 
even  surface  with  a  proper  grade  and  cross-section  is  obtained. 


292  THE  ART  OF  ROADMAKING 


OLD    EARTH    ROADBED 

Where  no  change  from  the  present  grade  of  those  portions  of  the  road 
not  already  surfaced  with  stone  is  shown  on  the  profile,  the  roadbed  is 
to  be  shaped  to  the  proper  cross-section  and  slight  elevations  with  con- 
tiguous depressions  removed  so  as  to  form  an  even  and  smooth  surface. 
The  roadbed  is  to  be  rolled  to  a  firm,  smooth  surface  before  the  appli- 
cation of  the  broken  stone. 

TRENCH    FOR    THE    BROKEN    STONE 

The  portion  of  the  roadbed  prepared  for  the  broken  stone  is  to  be 
below  the  sides  by  an  amount  equal  to  the  thickness  of  the  first  course 
of  stone  so  as  to  prevent  the  broken  stone  spreading  at  the  sides. 

SHAPE 

The  shape  for  the  roadbed  is  to  be  as  shown  on  the  accompanying 
plans,  and  is  to  have  a  cross  slope  of  -  —  inch  to  1  foot. 

FIRST  COURSE 
MATERIAL 

The  first  course  of  the  macadam  construction  is  to  consist  of  sound 
stone  broken  to  sizes  varying  from  3  inches  to  2  inches,  no  piece  to  have 
a  dimension  greater  than  3  inches.  This  is  to  be  known  as  "  No.  1 " 
size. 

No  material  is  to  be  used  which,  in  the  opinion  of  the  engineer,  is 
unfit  for  the  work.  If  any  such  material  is  put  upon  the  road  it  shall 
be  removed  immediately  upon  notice  from  the  engineer  and  replaced 
by  proper  material  at  the  contractor's  expense. 

SPREADING 

No  broken  stone  is  to  be  spread  before  the  roadbed  has  been  made  as 
specified. 

The  broken  stone  is  to  be  spread  upon  the  roadbed,  prepared  as  herein 
described,  with  shovels  from  piles  alongside  the  road  or  from  a  dumping 
board,  or  it  may  be  spread  directly  from  wagons  especially  constructed 
for  this  purpose  and  approved  by  the  engineer;  but  in  no  case  shall  the 
broken  stone  be  dumped  directly  upon  the  roadbed. 

ROLLING 

After  the  broken  stone  for  the  first  course  has  been  spread  to  an  uni- 
form thickness,  and  has  a  proper  cross-section,  it  is  to  be  rolled  with  a 
steam  roller,  weighing  not  less  than  10  tons,  until  it  is  compacted  to  form 


STATE  AID  LAWS  293 

a  firm,  smooth  surface.  Should  any  difficulty  be  experienced  while 
rolling  in  having  the  stone  readily  compact,  water  shall  be  sprinkled 
or  sand  or  other  material  be  spread,  as  the  engineer  may  direct.  The 
rolling  must  begin  at  the  sides  and  work  toward  the  center,  thoroughly 
covering  this  space  with  the  rear  wheel  of  the  roller. 

UNEVENNESS    OR    DEPRESSIONS 

Should  any  unevenness  or  depressions  appear,  during  or  after  the 
rolling  of  the  first  course,  they  are  to  be  remedied  immediately  with 
broken  stone  and  rerolled  until  a  firm,  even  surface  is  obtained. 

THICKNESS 

The  thickness  of  the  first  course  of  broken  stone,  after  thorough  rolling, 
is  to  be  that  of  the  class  of  macadam  construction*  specified  for  any 
particular  place  as  described  under  class  A,  B,  and  C. 

If,  for  any  reason,  a  greater  thickness  than  specified  is  made  by  the 
contractor  no  extra  allowance  for  such  additional  thickness  will  be  made. 

SHOULDERS 

After  the  first  course  has  been  made  as  herein  described  earth  shoulders 
are  to  be  constructed  along  each  side  of  the  road  for  a  width  of  at  least 
—  feet  as  shown  on  the  accompanying  plans. 

Against  these  shoulders  is  to  be  spread  the  broken  stone  for  the  second 
course  as  herein  described.  The  shoulders  are  to  contain  a  sufficient 
quantity  of  earth  so  that  a  smooth  and  continuous  slope  will  be  obtained 
after  the  shoulders  and  second  course  are  rolled.  The  shoulders  with 
the  -  -  feet  of  stone  will  make  a  total  width  of  -  -  feet  to  be 
shaped  with  a  cross  slope  of  —  —  inch  to  1  foot. 

Material  for  the  shoulders  must  be  free  from  roots,  stumps,  or  other 
vegetable  matter  and  thoroughly  compacted  by  the  roller.  Material 
with  a  proportion  of  sand  such  as  prevents  it  when  dry  compacting 
readily  under  the  roller,  is  not  to  be  used. 

No  material  which  is  considered  unfit  for  the  work  by  the  engineer 
is  to  be  used/and  where  any  such  is  put  on  the  work  it  shall  be  imme- 
diately removed,  upon  notice  by  the  engineer,  at  the  contractor's  expense. 

SECOND  COURSE 

The  second  course  of  the  macadam  construction  is  to  be  the  same 
width  as  the  first  course. 

MATERIAL 

The  second  course  is  to  consist  of  stone  broken  to  sizes  varying  from 
1  inch  to  2  inches;  no  piece  to  have  a  greater  dimension  than  2  inches. 
This  will  be  known  as  "  No.  2  "  size. 


294  THE  ART  OF  ROADMAKING 

Unless  otherwise  specified  the  stone  for  this  course  shall  be  trap  rock 
with  a  "coefficient  of  wear,"  as  determined  by  tests  made  at  the  lab- 
oratory of  the  highway  division  of  the  Maryland  geological  survey,  of 
not  less  than  15,  or  limestone  with  a  "coefficient  of  wear"  of  not  less 
than  10. 

SPREADING 

The  broken  stone  for  the  second  course  is  not  to  be  spread  before  the 
first  course  has  been  completed  and  shoulders  made  as  herein  specified. 

The  broken  stone  is  to  be  spread  upon  the  first  course,  prepared  as 
herein  described,  with  shovels  from  piles  alongside  the  road  or  from  a 
dumping  board,  or  it  may  be  spread  directly  from  wagons  especially  con- 
structed for  this  purpose  and  approved  by  the  engineer;  but  in  no  case 
shall  the  broken  stone  be  dumped  directly  upon  the  first  cour.se. 

ROLLING 

After  the  broken  stone  for  the  second  course  has  been  spread  to  a 
uniform  thickness,  and  has  a  proper  cross-section,  it  is  to  be  rolled  with 
a  steam  roller,  weighing  not  less  than  ten  tons,  until  it  is  compacted 
to  form  a  firm,  smooth  surface.  Should  any  difficulty  be  experienced 
while  rolling  in  having  the  stone  readily  compact,  water  shall  be  sprinkled, 
or  sand  or  other  material  be  spread,  as  the  engineer  may  direct. 

The  rolling  is  to  begin  at  the  sides,  the  shoulders  first  being  rolled 

firm  so  as  to  prevent  spreading  of  the  broken  stone  in  the  second  course. 

When  completed  the  surface  of  the  shoulders  and  of  the  second  course 

of  broken  stone  should  be  smooth  and  continuous  with  a  cross  slope  of 

—  inch      to  1  foot. 

UNEVENNESS    AND    DEPRESSIONS 

If  any  unevenness  or  depressions  appear  during  or  after  the  rolling 
of  the  second  course,  either  on  the  surface  of  the  shoulder  or  the  broken 
stone,  suitable  material  shall  be  added  to  remove  all  such  unevenness 
or  depressions,  earth  being  used  on  the  shoulders  and  No.  2  stone  for 
the  broken-stone  surface. 

THICKNESS 

The  thickness  of  the  second  course  of  broken  stone,  after  thorough 
rolling,  is  to  be  that  of  the  class  of  macadam  construction,  specified  for 
any  particular  place,  as  described  under  classes  A,  B,  and  C. 

If,  for  any  reason,  a  greater  thickness  than  specified  is  made  by  the 
contractor,  no  extra  allowance  for  such  additional  thickness  will  be 
made. 


STATE  AID  LAWS  295 


THIRD  COURSE 
MATERIAL 

The  third  course  of  the  macadam  construction  is  to  consist  of  trap 
rock  screenings  varying  in  size  from  dust  to  1-inch  pieces.  Other  material 
than  trap  rock  screenings  may  be  used  if  approved  by  the  engineer. 
Limestone  screenings  shall  be  used  with  a  limestone  second  course. 

SPREADING 

After  the  second  course  of  No.  2  stone  has  been  rolled  and  completed 
as  above  described  the  screenings  are  to  be  spread,  but  in  no  case  are 
screenings  to  be  used  until  the  second  course  has  been  thoroughly  rolled 
and  compacted.  The  screenings  are  to  be  spread  dry  with  shovels  from 
piles  alongside  the  road,  or  from  dumping  boards,  but  in  no  case  are  the 
screenings  to  be  dumped  directly  on  the  second  course.  The  quantity 
of  screenings  used  is  to  be  such  as  will  just  cover  the  second  course. 

WATERING    AND    ROLLING 

After  the  screenings  are  spread  they  are  to  be  sprinkled  with  water 
from  a  properly  constructed  sprinkling  cart,  and  then  rolled  with  a  steam 
roller  weighing  not  less  than  ten  tons.  The  amount  of  water  necessary 
is  to  be  determined  by  the  engineer.  The  rolling  is  to  begin  at  the  sides 
and  to  continue  until  the  surface  is  hard  and  smooth  and  shows  no  per- 
ceptible tracks  from  vehicles  passing  over  it. 

If,  after  rolling  the  screenings,  the  No.  2  stone  appears  at  the  surface, 
additional  screenings  shall  be  used  in  such  places. 

The  rolling  and  watering  shall  continue  until  the  water  flushes  to  the 
surface.  The  rolling  is  to  extend  over  the  whole  width  of  the  road, 
including  the  shoulders. 

UNEVENNESS    AND     DEPRESSIONS 

If  any  unevenness  or  depressions  appear  in  the  road  surface  after 
rolling  the  screenings,  No.  2  broken  stone  and  screenings  shall  be  used 
until  they  are  removed  and  the  finished  surface  conforms  to  the  proper 
cross-section,  as  shown  on  the  accompanying  plans,  and  presents  a 
smooth,  even  appearance. 


PART  III 
CITY  STREETS  AND  PAVEMENTS 


CHAPTER  XIII 
THE  DESIGN   OF   CITY  STREETS* 

MOST  cities  grow  up  gradually,  without  any  comprehensive 
or  prearranged  street  plan,  and  without  adequate  regulations 
governing  suburban  development.  Streets  are  laid  out  in 
the  interests  of  individuals,  and  cities  are  developed  under 
the  stimulus  of  real  estate  speculation,  regardless  of  the 
interests  of  the  public.  It  is  usually  after  the  city  has  grown 
to  a  considerable  size,  that  the  remedy  is  applied  for  this 
ungoverned  development,  and  in  some  instances  cities  have 

spent  vast  sums  in  correcting  what  might  have 
Objects  in  been  prevented  by  an  adequate  plan  of  street  design, 
cit^streets  -^n  plannmg  the  streets  of  a  city,  the  objects  to 

be  kept  in  mind  are: 

1.  The  subdivision  of  the  area  to  give  the  maximum  effi- 

ciency for  business  and  residence  purposes. 

2.  Sufficient  accommodation  for   the  pedestrian  and  vehic- 

ular traffic  on  the  streets. 

3.  Good    drainage    and    easy    communication   between   the 

different  parts  of  the  city. 

In  the  subdivision  of  the  area,  it  is  desirable  to  make  the 
size  of  lots  such  that  few  of  them  will  be  further  subdivided, 
as  clearness  of  identity  is  always  maintained  by  referring 

*  Prof.  I.  O.  Baker,  in  his  "Roads  and  Pavements,"  deals  more 
thoroughly  than  any  other  writer  with  this  feature  of  municipal  work. 

296 


THE  DESIGN  OF  CITY  STREETS  297 

to  the  original  number  in  transferring  or  assessing  the  property. 
Experience  has  shown  that  a  frontage  of  25  feet  and  a  depth 
of  from  100  to  150  feet  is  the  best.  This  size  is  suitable  for 
business  purposes,  and  for  residence  streets  two  or  more  lots 
give  proper  grounds. 

With  a  rectangular  system  of  streets,  the  blocks  are  pref- 
erably long  and  narrow,  since  the  distance  required  between 
streets   in  one  direction  is  only  that  necessary  to 
give  the  proper  depth  of  lots,  while  in  the  other          blocks 
direction  the  streets  need  be  only  close  enough  to 
provide    convenient    channels    for   the    traffic.     For    conven- 
ience, especially  in  business  districts,  it  is  best  to  have  an 
alley,  from   16  to  20  feet  wide,  run  lengthwise  through  the 
block. 

Sizes  of  blocks  vary  in  any  particular  city  and  still  more 
between  different  cities.  The  following  are  the  sizes  of  some 
typical  blocks: 

Boston 200X400  ft.  and  100X550  ft. 

New  York 200X900  "   and  200X400  " 

Philadelphia 400X500  "   and  500X800  " 

Washington 400X600  "  and  300X800  " 

Montreal 250x750  " 

Chicago 300X350  "   and  300x500  " 

Fig.  165  is  given  by  Baker  *  to  illustrate  the  advantages 
to  be  derived  from  a  careful  study  of  the  best  size  of  blocks 
and  of  the  most  advantageous  arrangement  of  streets.  The 
left-hand  side  of  the  diagram  shows  the  typical  arrangement 
of  streets  and  blocks  in  the  residence  district  of  New  York 
City,  the  shaded  portions  representing  the  usual  buildings. 
Here  the  three  center  blocks  comprise  an  area  of  720X800 
feet,  and  contain  480,000  sq.ft.  of  building  area  and  96,000 
sq.ft.  of  streets.  The  right-hand  side  shows  a  much  superior 
arrangement  in  which  in  a  corresponding  area  there  are 
481,000  sq.ft.  of  building  area  and  94,200  sq.ft.  of  streets. 

*  "  Roads  and  Pavements/'  p.  309. 


298 


THE  ART  OF  ROADMAKING 


The  two  plans,  therefore,  give  substantially  the  same  area 
for  buildings  and  for  streets.  In  the  first  case  the  length  of 
streets  is  1,600  feet,  in  the  second  1,520  feet;  therefore  the 
two  plans  have  practically  equal  light  and  air,  but  the  second 
arrangement  is  the  better  in  the  following  particulars: 

1.  Number  of  corner  sites. 

2.  Accessibility  of  rear  entrances  for  delivery  of  provisions, 


600  ff 


STRE.ET 


STREET 


STREET 


STREET 


8 


STREET 


FIG.  165. — Improved  Arrangement  of  Streets  and  Blocks. 

coal,   etc.,   and   the   removal   of  garbage,   ashes,   etc., 
and  in  case  of  fire. 

3.  Removal  from  the  street  of  dangerous  and  cramped  cellar 

entrances. 

4.  Removal   from   the   main    and    primary    streets    of   the 

loading  and  unloading  of  trucks. 

5.  Increased    transportation   facilities    in    a    direction    per- 

pendicular to  the  length  of  the  original  blocks. 
In  planning  a  system  of  streets,  drainage  and  easy  com- 
munication between  the  different  sections  of  the  city  should 


THE  DESIGN  OF  CITY  STREETS  299 

be  carefully  considered.  Surface  drainage,  sewerage  and 
traffic  must  follow  the  general  slope  of  the  land, 
and  therefore  if  there  is  much  irregularity  of  ^^°n  °f 
contour  in  the  site,  a  location  of  the  streets  with 
reference  to  the  contours  will  afford  at  once  the  best  drainage 
and  the  easiest  communication  between  different  parts  of 
the  city.  If  the  site  is  nearly  level,  the  relationship  between 
the  slope  of  the  land  and  the  direction  of  the  streets  is  com- 
paratively unimportant;  but  the  arrangement  of  the  street 
plan  to  afford  the  greatest  facilities  for  communication  between 
the  different  parts  of  the  city  is  still  an  important  matter. 
The  conclusion  is,  therefore,  that  on  a  site  of  irregular  con- 
tour, the  streets  should  be  located  with  reference  chiefly  to 
the  topography,  and  on  a  level  site  primarily  to  secure  the 
most  direct  and  easiest  intercommunication. 

Surface  drainage,  sewerage  and  traffic  should  follow  the 
slope  of  the  country,  and  any  attempt  to  deviate  from  this 
becomes  a  serious  question  in  the  building  of  a  city  upon  any 
but  nearly  level  ground.  The  streets  are  of  necessity  the 
drainage  lines  of  the  city  and  should  be  placed  in  the  natural 
valleys,  and  the  failure  so  to  locate  the  streets  in  many  cities 
where  the  land  is  very  irregular  in  contour  has  led  to  great 
expense  in  the  construction  of  the  streets  and  of  a  system 
of  storm-water  sewers.  The  upper  half  of  Fig.  166  shows 
an  actual  case  of  a  system  of  rectangular  streets  located  with- 
out any  reference  to  the  topography  of  the  site;  and  the 
lower  half  of  the  same  diagram  shows  a  proposed  arrangement* 
that  would  save  much  expense  in  grading  the  streets  and  at 
the  same  time  give  a  quick  entrance  into  the  center  of  the 
city,  and  also  long  easy  grades  from  the  heart  of  the  city 
to  the  higher  outlying  districts. 

There  are  three  distinct  general  plans  for  location  of  city 
streets  with  reference  to  directness  and  ease  of  communica- 
tion. One  consists  of  a  system  of  parallel  streets  crossing  a 
similar  system  at  right  angles,  often  called  the  "checker- 
board," but  more  properly  the  "rectangular"  system,  since 

*  By  \V.  D.  Elder,  in  Proc.  Mich.  Eng.  Soc.,  1898,  p.  52. 


300 


THE  ART  OF  ROADMAKING 


1 


JL 


I         1 1         II         II         |l         I 


\ 


FIG.  166. — Location  of  Streets  with  Reference  to  Contours. 


THE  DESIGN  OF  CITY  STREETS  301 

the   blocks    are   not    necessarily  square.     This   arrangement, 
which    is    the  most    common,  gives    a   maximum    General 
area  for  blocks,  and  also   furnishes  blocks  of  the    plans  for 
best  form  for  subdivision  into  lots.      The  second    location  of 
arrangement  of  streets    consists  of    a    rectangular 
system  with  occasional  diagonal  streets  along  the  lines  of  maxi- 
mum travel.     This  system,  sometimes  called  the  " diagonal" 
system,  was  employed  by  L7 Enfant  in  planning  the  city  of 
Washington,  and  to  a  limited  degree,  was  adopted  in  laying 
out  the  city  of  Indianapolis,  which  has  four  broad  diagonal 
avenues  converging  to  a  circular  park  in  the  center. 

The  chief  advantage  of  the  diagonal  streets  is  the  economy 
due  to  the  saving  of  distance  by  traversing  the  hypothenuse 
instead  of  the  two  sides  of  a  right  triangle.  The  two  American 
cities  mentioned  are  the  only  places  of  importance  in  which 
the  system  was  adopted  in  advance  of  the  building,  but  in 
Rome,  London,  Paris,  and  in  numerous  smaller  places  in 
Europe,  whole  districts  have  been  razed  to  make  way  for  new 
streets  to  serve  as  arteries  for  increased  traffic.  A  second, 
and  by  no  means  an  unimportant  advantage  of  the  diagonal 
system,  is  the  open  squares  and  spaces  so  grateful  to  the  eye 
and  in  compactly  built  cities  of  no  little  sanitary  value. 

Although  the  diagonal  avenue  occupies  ground  that  might 
otherwise  be  used  for  building  purposes,  there  is  a  compensat- 
ing advantage  in  the  greater  length  of  street  front  obtained.* 
In  many  cases  the  total  cost  of  cutting  diagonal  streets  through 
built-up  districts  has  been  paid  by  the  increased  value  of 
the  property  on  and  near  the  street  thus  opened  up. 

The  third  arrangement  of  city  streets  is  the  "ring"  pr 
"concentric"  plan,  which  is  very  popular  in  Europe.  The 
most  noted  example  is  Vienna  with  its  Ring-strasse  (Ring 
street)  within  and  its  Gurtel-strasse  (Girdle  street)  without. 
The  former  is  187  feet  wide  and  encircles  the  public  buildings 
and  the  leading  houses  of  business  and  amusement.  The 
enclosed  network  of  streets  intersect  the  Ring-strasse  at 


*  For  a  discussion  of  this  phase  of  the  subject,  see  an  article  by  L. 
M.  Haupt,  in  Journ.  Franklin  Inst.,  Vol.  103,  p.  252. 


302 


THE  ART  OF  ROADMAKING 


DDDCSX  -  a0 
aoMl 

'QQ 


|| — ii — i^  ' — »^nr~)ni7/ini— \  i — 1| 

FIG.  167.— Street  Plan  of  Washington,  D.  C. 


THE  DESIGN  OF  CITY  STREETS  303 

forty  points,  and  outward  from  it  extend  fifteen  main  radial 
avenues. 

The  width  of  city  streets  is  important  on  account  of  its 
influence  upon  the  ease  with  which  traffic  may  be  conducted 
and  also  because  of  its  effect  upon  the  health  and 
comfort  of  the  people  by  determining  the  amount 
of  light  and  air  which  may  penetrate  into  thickly 
built-up  districts.  The  streets  of  nearly  all  large  cities  are 
too  narrow,  being  crowded  and  dark.  A  more  liberal  policy 
in  planning  streets  would  probably  be  of  pecuniary  advantage, 
as  wide  streets  usually  give  a  high  financial  value  to  adjoining 
property.  A  lot  100  feet  deep  on  a  street  80  feet  wide  is 
usually  more  valuable  than  a  lot  110  feet  deep  on  a  street 
60  feet  wide;  that  is  to  say,  within  reasonable  limits  land  is 
usually  more  valuable  in  the  street  than  on  the  rear  of  the 
lot.  Wide  streets  are  especially  needed  where  they  are 
bordered  by  high  buildings  or  are  to  carry  street  railway 
lines. 

In  order  properly  to  accommodate  the  traffic  in  business 
districts  of  cities  of  considerable  size,  a  street  should  have 
a  width  of  100  to  140  feet,  the  whole  of  it  being  used  for 
roadway  and  side-walks;  while  residence  streets  in  a  city 
of  considerable  size,  where  the  houses  are  set  out  to  the 
property  line  and  stand  close  together,  should  have  a  width 
of  60  to  80  feet.  Although  it  is  advantageous  to  have  a 
wide  street,  it  is  not  necessary,  nor  even  desirable,  that  the 
whole  width  be  paved;  the  central  portion  may  be  paved, 
a  strip  on  either  side  being  reserved  for  grass  plats.  The 
width  of  the  pavement  should  be  adjusted  to  the  amount  of 
traffic,  which  Varies  greatly  accordingly  as  the  street  is  a 
business  street,  a  thoroughfare,  or  an  unfrequented  residence 
street. 

The  width  of  the  streets  in  different  cities  varies  greatly. 
In  the  older  places  in  New  England  and  the  Central  States, 
many  of  the  streets  are  only  30  to  40  feet  wide;  but  in  the 
West  a  street  is  seldom  less  than  60  to  66  feet  wide.  In  both 
regions  the  principal  streets  are  often  80  to  100  feet  wide, 
and  in  many  of  the  larger  cities  the  boulevards  and  great 


304  THE  ART  OF  ROADMAKING 

avenues  are  150  to  180  feet.  The  main  avenues  in  Washing- 
ton are  160  feet  wide,  in  New  York  135,  and  in  Boston  180 
feet. 

At  present  the  regulations  governing  the  width  and  the 
arrangements  of  additions  and  subdivisions  of  Washington, 
a  city  which  has  the  best  street  plan  of  any  in  America,  are: 

"No  new  street  can  be  located  less  than  90  feet  in  width, 
and  the  leading  avenues  must  be  at  least  120  feet  wide.  Inter- 
mediate streets  60  feet  wide,  called  places,  are  allowed  within 
blocks;  but  full- width  streets  must  be  located  not  more 
than  600  feet  apart." 

The  proportion  of  the  area  of  the  city  devoted  to  streets 
varies    greatly,    particularly    between    the    older 

Area  of  ^   ^     newer   cities.     The   following   is   the    per 

streets. 

cent    of   street    area    in    a   few    extreme    cases    of 

American  cities:* 

Minimum  Street  Per  Maximum  Street  Per 

Area.  Cent.  Area.  Cent. 

1.  Taunton,  Mass 3.20     Duluth,  Minn 86.7 

2.  Worcester,  Mass 5.43     Dallas,  Tex 78.3 

3.  Binghamton,  N.  Y 7.55     Denver,  Colo 73.9 

4.  Philadelphia,  Pa 8.42     Indianapolis,  Ind 56.4 

5.  Boston,  Mass 8.76     Washington,  D.  C 43.5 

6.  Lowell,  Mass 8.92     Davenport,  la 42.1 

7.  Fall  River,  Mass 9.17     Evansville,  Ind 40.8 

The  area  devoted  to  streets  and  alleys  in  a  few  of  the 
principal  cities  of  the  world  is  as  follows: 

Area  of  Streets  and  Alleys.  Per  Cent. 

1.  Washington 54 

2.  Vienna 35 

3.  New  York  City 35 

4.  Philadelphia 29 

5.  Boston 26 

6.  Berlin 26 

7.  Paris 25 

*  Census  Bulletin,  No.  100,  July  22,  1891,  p.  16. 


THE  DESIGN  OF  CITY  STREETS  305 

TABLE  XV 

ACRES   REQUIRED  PER  MlLE  FOR  DIFFERENT  WlDTHS  OF  ROADWAY. 


Width. 
Feet. 

Acres 
per  mile. 

Width. 
Feet. 

Acres 
per  mile. 

Width. 
Feet. 

Acres 
per  mile. 

Width. 
Feet. 

Acres 
per  mile. 

Width. 
Feet. 

Acres 
per  mile. 

* 

.030 

19 

2.30 

40 

4.85 

59 

7.15 

80 

9.70 

* 

.061 

20 

2.42 

41 

4.97 

60 

7.27 

81 

9.82 

1 

.121 

21 

2.55 

41* 

5.00 

61 

7.39 

82 

9.94 

2 

.242 

22 

2.67 

42 

5.09 

62 

7  52 

824 

10.00 

3 

.364 

23 

2.79 

43 

5.21 

63 

7.64 

83 

10.  OS 

4 

.485 

24 

2.91 

44 

5.33 

64 

7.76 

84 

10.18 

5 

.606 

24| 

3.00 

45 

5.45 

65 

7.88 

85 

10.30 

6 

.727 

25 

3.03 

46 

5.58 

66 

8.00 

86 

10.42 

7 

.848 

26 

3.15 

47 

5.70 

67 

8.12 

87 

10.54 

8 

.970 

27 

3.27 

48 

5.82 

68 

8.24 

88 

10.66 

8* 

1.00 

28 

3.39 

49 

5.94 

69 

8.36 

89 

10.78 

9 

1.09 

29 

3.52 

49* 

6.00 

70 

8.48 

90 

10.90 

10 

1.21 

30 

3.64 

50 

6.06 

71 

8.61 

90f 

11.00 

11 

1.33 

31 

3.76 

51 

6.18 

72 

8.73 

91 

11.03 

12 

1.46 

32 

3.88 

52 

6.30 

73 

8.85 

92 

11.15 

13 

1.58 

33 

4.00 

53 

6.42 

74 

8.97 

93 

11.27 

14 

1.70 

34 

4.12 

54 

6.55 

74i 

9.00 

94 

11.39 

15 

1.82 

35 

4.24 

55 

6.67 

75 

9.09 

95 

11.51 

16 

1.94 

36 

4.36 

56 

6.79 

76 

9.21 

96 

11.63 

16* 

2.00 

37 

4.48 

57 

6.91 

77 

9.33 

97 

11.75 

17 

2.06 

38 

4.61 

57* 

7.00 

78 

9.45 

98 

11.87 

18 

2.18 

39 

4.73 

58 

7.03 

79 

9:58 

99 

12.00 

100 

12.12 

It  is  wise  to  make  the  streets  of  residence  districts  of  liberal 
width  for  sanitary  and  aesthetic  reasons,  and  also  because 
the  future  of  the  street  cannot  be  certainly  fore- 
seen— the  residence  street  may  become  a  business    Wldth  of 

pavement, 
street,   or   an  unfrequented  street  a  thoroughfare. 

However,  it  is  not  necessary  that  the  whole  width  should  be 
devoted  to  wheelways  and  sidewalks,  particularly  in  small 
cities.  A  grass  plat  between  the  sidewalk  and  the  pavement, 
in  which  shade  trees  are  set,  adds  to  the  beauty  of  the  street 
and  to  the  comfort  of  the  residents,  by  removing  the  houses 
farther  from  the  noise  and  dust  of  the  pavement.  The  grass 
plat,  or  parking,  also  affords  an  excellent  place  in  which  to 
place  water  or  gas  pipes,  telephone  and  electric-light  conduits, 
etc.  In  large  cities  where  the  street  front  is  built  up  solid 
with  houses  of  several  stories,  it  may  be  necessary  to  dispense 
with  the  grass  plat,  and  devote  the  entire  street  to  sidewalks 
and  roadway. 


306  THE  ART  OF  ROADMAKING 

For  some  reason,  it  has  long  been  the  custom  to  pave  streets 
from  curb  to  curb.  Possibly  this  practice  grew  out  of  the 
necessity  of  paving  business  streets  from  curb  to  curb,  and 
as  business  streets  are  the  first  to  be  paved  in  every  city, 
it  was  not  unnatural  that  when  later  the  residence  streets 
were  also  paved,  similar  designs  prevailed.  The  idea  that 
all  of  the  street  must  be  paved  is  often  shown  in  the  sudden 
increase  in  the  width  of  metalled  roadway,  where  a  macadam 
road  enters  a  city.  Thus,  on  several  of  the  streets  in  Rochester, 
N.  Y.,  the  width  of  macadam  is  more  than  double  the  width 
of  macadam  on  the  road  just  beyond  the  city  limits,  and  that 
this  practice  is  widespread  is  shown  by  the  reports  of  many 
city  engineers. 

There  is  little  justification  for  the  expenditure  of  money 
involved  in  paving  residence  streets  their  full  width;  rarely  is 

iv-n  in  there  a  residence  street  where  traffic  is  great 
middle  of  enough  to  justify  a  paved  trackway  greater  than  16 
road  or  18  feet  in  width,  and  if  the  passing  vehicles  on 

destructive.  any  res^ence  street  are  watched  it  is  seen  that  they 
cling  closely  to  the  center.  No  argument  will  convince  the 
public  that  it  is  poor  pavement  economy  to  always  travel  in 
the  one  narrow  path,  and  in  spite  of  signs,  and  warning 
notices,  both  horse  and  driver  will  continue  to  use  the  cen- 
ter of  the  road.  The  horse  finds  it  easier  travelling  in  the 
center  where  all  four  feet  are  on  a  level,  and  the  driver  finds 
it  pleasanter  riding  where  the  seat  is  also  level;  so  animal 
and  human  comfort  take  precedence  over  pavement  economics. 
Some  time  ago  the  Massachusetts  board  of  highway  commis- 
sioners caused  to  be  erected  along  the  highways  of  that  state 
signs  requesting  drivers  of  all  kinds  of  vehicles  not  to  drive 
in  the  middle  of  the  road.  This  action  was  taken  because 
driving  in  the  center  of  the  road  was  believed  to  be  respon- 
sible for  the  heavy  repair  expenditure  necessary.  After 
the  sign  idea  had  been  given  a  fair  trial  the  commis- 
sioners reported  that  the  cost  of  repairs  was  much  less  where 
the  order  was  obeyed  than  where  it  was  disregarded.  Fig. 
168  shows  such  a  sign  on  a  state  highway  near  Sterling,  Mass. 

Since,  then,  the  center  of  a  street  receives  practically  all  the 


THE  DESIGN  OF  CITY   STREETS 


307 


WORCESTER-* 
WESTBOYLSTON 
CAMPGROUND 

If  PRINCETON 
WEST  STERLING 


travel,  there  seems  little  reason  for  paving  areas  seldom  used 
except  by  occasional  carriages  and  delivery  wagons  stopping 

in    front    of    houses.      This    area  ^ 

might  economically  be  left  un- 
paved,  as  an  earth  road  is  usually 
only  very  bad  during  the  wet  season 
of  the  year,  and  then  its  badness 
varies  directly  with  the  amoun^  of 
traffic  that  it  must  bear.  It  is  not 
the  occasional  passing  of  a  wheel 
over  an  earth  road  that  cuts  it 
into  ruts,  but  the  repeated  passage 
of  many  wheels  which  churn  the 
water  and  the  earth  together,  until 
deep  ruts  are  formed  ready  to  re- 
ceive the  very  next  fall  of  rain  and 
store  it  there. 

In  Venice,  California,  a  sea-side 
town  fifteen  miles  from  Los  Angeles, 
center-walks  have  superseded  side- 
walks. 

The   innovation   practically  con- 
verts the  many  short  streets   lead- 
ing   from   the   ocean    front    into    recreation    grounds,  where 
children  may  play  in  safety  without  fear  of  being  Center. 
dispersed     or    injured    by    passing    vehicles.     By  walks 
mutual  agreement  between  the  property  owners  and  instead  of 
the  city   officials,  all   vehicular  traffic  is  excluded  S1  ewa    s' 
from   certain  streets,   the  tradesmen  and  others    being   rele- 
gated to  the  use  of  20-foot  alleys  which  abut  upon  the   rear 
of  all  lots  fronting  upon  the  cross  streets. 

Park  avenue,  shown  in  the  accompanying  view,  is  one  of  over 
thirty  streets  which  have  been  improved  at  the  expense  of 
the  abutting  property  owners  with  the  centerwalk  system. 

From  houseline  to  houseline,  the  "  street "  is  40  feet  in  width, 
extending  350  feet  at  right  angles  with  the  ocean.  The  walk 
down  the  center  varies,  according  to  the  choice  of  property 
owners,  from  10  to  15  feet  in  width.  It  is  laid  strictly  according 


FIG.  168. 


308 


THE  ART  OF  ROADMAKING 


THE  DESIGN  OF  CITY  STREETS  309 

to  specifications,  recommended  by  the  city  engineer,  approved 
by  the  board  of  trustees  and  filed  at  the  city  hall. 

The  specifications  call  for  3^-inch  concrete  foundation,  laid 
upon  the  sand  composing  the  street.  No  joints  are  permitted, 
except  where  work  is  stopped  from  day  to  day,  and  at  such 
points  a  reinforcement  of  chicken-wire  must  be  laid,  the  full 
width  of  the  walk,  wrhere  the  concrete  work  is  renewed. 

The  specifications  also  call  for  a  continuous  strip  of  chicken- 
wire  netting  reinforcement,  3  feet  wide,  of  not  more  than  3-inch 
mesh,  on  each  side  of  the  center  line  of  the  walk,  midway 
between  the  middle  and  the  outer  edge. 

On  top  of  the  concrete  base  is  spread  a  ^-inch  finishing  coat, 
composed  of  equal  parts  of  cement  and  sand.  The  surface  is 
neatly  marked  off  in  squares,  while  moist,  and  coloring  matter, 
usually  red  or  slate  gray,  is  added  to  give  the  finished  walk 
any  hue  desired. 

One  detail  of  the  specifications,  which  tends  to  guarantee 
good  wrorkmanship,  is  the  direction  that  the  contractor  must 
stamp  his  name  in  letters  not  less  than  f-inch  in  height  and 
i-inch  deep  in  the  pavement  at  least  once  in  every  60  linear 
feet  of  the  work. 

In  the  pavement  shown  herewith,  the  contract  figures  for 
the  walk  were  12  cents  per  square  foot  for  the  pavement 
and  16  cents  per  linear  foot  for  the  curbing.  The  latter,  in 
most  instances,  is  made  a  part  of  the  walk,  extending  down 
into  the  sand  on  either  side  for  6  or  8  inches,  thus  acting  as  an 
anchor  for  the  whole. 

AVith  the  exception  of  a  few  thoroughfares  which  connect 
with  county  roads  in  the  interior,  all  of  the  streets  bordering 
upon  the  waterfront  in  Venice  have  been  paved  with  a  center- 
walk,  built  either  of  concrete  or  wood. 

Freedom  from  the  noise  of  passing  vehicles,  with  the 
consequent  clouds  of  dust;  the  safety  and  comfort  of  residents 
and  the  exceptional  opportunity  for  ornamental  effects  offered 
by  the  exclusion  of  traffic  and  the  conversion  of  the  roadways 
into  footways  are  distinctions  peculiar  to  this  system  of  street 
design. 

It  is  universally  admitted  that  pavements  are  desirable; 


310  THE  ART  OF  ROADMAKING 

but  often,  owing  to  the  unwillingness  of  at  least  some  of  the 
people  to  pay  for  them,  or  to  the  idea  of  some  that  they  must 
have  a  pavement  from  curb  to  curb  or  none  at  all,  it  is  diffi- 
cult to  secure  them.  Within  reasonable  limits  of  cost  wide 
pavements  are  desirable,  but  length  is  more  valuable  than 
width.  Excessive  width  delays  or  prevents  the  getting  of  any 
pavement  at  all;  hence  one  help  toward  securing  a  pavement 
is  to  make  the  pavement  only  wide  enough  to  accommodate 
the  traffic.  A  narrow  pavement  not  only  costs  less  to  con- 
struct, but  also  costs  less  to  clean,  while  the  cost  of  mainte- 
nance depends  chiefly  (or,  with  a  pavement  not  subject  to 
natural  decay,  wholly)  upon  the  amount  of  traffic  and  hence 
is  practically  independent  of  the  width. 


CHAPTER  XIV 
STONE    BLOCK    PAVEMENTS 

STONE  in  a  variety  of  forms  has  been  used  for  paving 
purposes  from  the  earliest  times.  In  the  form  of  blocks  its 
earliest  systematic  use  was  by  the  Romans,  whose  roads 
were  practically  works  of  solid  masonry  construction,  built 
of  irregularly  shaped  stones,  but  finished  to  a  smooth  and 
true  surface.  These  roads  were  wasteful  of  material  but  were 
remarkable  for  their  strength,  durability  and  excessive  cost, 
which,  however,  was  principally  in  the  lives  of  captives,  who 
were  forced  to  build  these  highways  for  the  armies  of  their 
conquerors. 

Under  Julius  Caesar,  Rome  was  in  complete  communication 
with  all  the  principal  cities  of  its  great  empire  by 
such   paved   roads,    which    were    distinguished    by 
the     names     Via,    Actus,     Iter,    Semita,     Trames, 
Diverticulum,  Divertium,  Callais,  etc. 

The  Via  corresponded  with  our  common  roads,  and  had  a 
width  of  8  Roman  feet. 

The  Via  Mililari  and  other  important  roads  in  the  neighbor- 
hood of  Rome  had  a  double  width,  16  Roman  feet  (15  ft.  6  ins. 
English),  and  margines,  or  sidewalks,  8  feet  wide.  The  middle, 
convex  portion  was  paved  with  blocks  and  divided  from  the 
sidewalks  by  a  curb  of  low  wall,  2  feet  wide  and  18  inches 
high.  The  middle  was  for  the  infantry;  the  margines  for  car- 
riages and  equestrians. 

The  Actus  was  4  feet  wide,  for  single  carriages. 

The  Iter,  for  horsemen,  pack  animals,  and  pedestrians,  the 
width  of  which  was  3  feet.  Semita  was  only  half  the  breadth 
of  the  Iter,  and  was  called  Diverticulum,  or  Divertium  when  it 
branched  across  fields.  The  Semita  on  steep  grades  was 
frequently  in  the  form  of  steps. 

311 


312  THE  ART  OF  ROADMAKING 

The  Callais  was  a  mountain  path,  used  principally  by 
shepherds. 

The  Via  Appia,  Appian  Way,  was  not  only  the  earliest 
military  road,  but  the  best  constructed.  It  extended  from 
Rome  to  Brindusium  (now  Brindisi),  a  distance  of  360  miles, 
and  was  constructed  principally  by  Julius  Caesar.  The  mode 
of  construction,  which  was,  in  general,  the  same  as  used  in  all 
important  military  roads,  was  as  follows: 

The  course  being  decided  upon,  in  as  nearly  straight  lines 
as  possible,  it  was  marked  by  two  parallel  trenches  excavated 
at  varying  distances  apart  according  to  the  importance  of  the 
highway.  This  also  showed  the  nature  of  the  subsoil,  from 
which  the  level  of  the  foundations  was  determined;  all  unsta- 
ble materials  were  rem'oved  to  a  depth  of  about  3  feet,  the 


f:?. 


FIG.  170. — Cross-section  of  Roman  Road  (Appian  Way). 

bottom  was  consolidated  by  ramming  until  a  solid  foundation 
was  obtained.  In  this  undrained  trench  the  road  materials 
were  placed  in  more  or  less  regular  layers. 

The  statumen,  or  base,  consisted  of  two  courses  of  large  flat 
stones  laid  in  lime  mortar,  and  was  usually  about  15  inches 
thick.  Upon  this  was  laid  the  rudus,  or  rubble,  consisting  of 
a  9-inch  course  of  small  fragments  of  stone  embedded  in  suffi- 
cient lime  mortar  to  fill  their  voids. 

Upon  this,  the  nucleus  was  formed  of  fragments  of  gravel, 
stone,  pottery  and  brick  mixed  with  lime  mortar  to  form  a 
concrete,  which  was  laid  while  hot  and  consolidated  by  ram- 
ming, and  was  made  about  6  inches  thick.  The  summa 
crusta  (top  crust)  or  pavimentum  (hard  surface)  was  formed 
of  closely  jointed,  irregular  stones,  which  formed  a  mosaic 
about  6  inches  thick,  the  top  of  which  was  practically  on  a 
level  with  the  adjoining  natural  surface  of  the  ground. 


STONE  BLOCK  PAVEMENTS 


313 


In  and  near  the  cities  the  pavimentum  was  formed  of  larger 
irregular  blocks  of  basalt,  or  porphyry  or  lava,  2  to  2^  feet  in 
length  and  width  and  12  inches  to  15  inches  in  thickness, 
which  were  dressed  and  fitted  together  with  extreme  accuracy 
and  were  bedded  in  cement.  On  these  roads  were  carried 
huge  columns,  obelisks,  and  other  blocks  weighing  hundreds 
of  tons,  without  any  injury  to  the  surface. 

The  earliest  pavements  were  constructed  in  almost  every 
case  of  rough  stone,  which  were  the  most  available  and  at  the 
same  time,  most  durable.  As  the  need  for  better  pavements 
increased  with  the  growth  of  cities,  the  rough  cobble-stone 
was  gradually  superseded  by  stones  formed  into  the  shape  of 
blocks  which  gave  a  comparatively  smooth  surface.  This  was 
the  beginning  of  the  modern  stone-block  pavement,  and  in 


u^;'?&^^ 


FIG.  171. — Cross-section  of  Cobblestone  Pavement. 


European  countries  the  pavements  have  improved  until  they 
had  developed  into  something  of  a  standard  made  of  blocks 
about  6  by  8  inches  square,  and  of  depths  varying  according 
to  the  traffic. 

In  this  country,  however,  the  original  pavements  were  all 
of  cobble.     Most   of  the  cities  were  poor  and  the 
cobblestones  being   available   and  cheap,  naturally 


Cobblestone 
pavement. 


came    into    quite    common  use.     They  gave  good 
service,  but  were  rough,  uneven  and  very  noisy. 

Little,  if  any,  cobblestone  pavement  is  now  being  laid. 
In  a  few  localities  where  the  property  owners  pay  the  first 
cost  and  are  then  relieved  of  further  cost  of  maintenance  or 
relaying,  its  cheapness  has  been  a  sufficient  inducement  to 
cause  it  to  be  used,  but  is  never  gives  satisfaction  and  is  really 
only  a  makeshift  for  a  pavement.  In  the  days  when  pave- 


314  THE  ART  OF  ROADMAKING 

ments  of  this  class  were  extensively  laid  and  the  demand  for 
the  stones  became  so  great  that  suitable  ones  were  obtained 
only  at  considerable  expense  and  with  some  difficulty,  almost 
anything  in  shape  and  size  was  permitted  to  be  used,  and  the 
specifications  were  most  shamefully  abused.  The  result  was 
that  cobblestone  pavements  were  even  worse  than  they  would 
have  been  had  they  been  properly  laid.  The  specifications 
generally  provided  that  the  stones  should  be  the  best  selected 
water  or  bank  cobblestones,  of  a  durable  and  uniform  quality, 
with  round  heads  and  well-shaped  large  ends.  They  should 
be  not  less  than  4  inches  nor  more  than  8  inches  in  diameter 
across  the  head,  nor  less  than  5  inches  nor  more  than  10  inches 
in  depth;  no  triangular,  split  or  otherwise  ill-shaped  stones 
should  be  used,  nor  any  which  are  soft  or  rotten. 

Since  the  introduction  of  asphalt  and  brick  pavements  and 
since  the  decrease  in  the  cost  of  stone-block  pavement  by  the 
introduction  of  improved  methods  of  quarrying,  and  in  the 
cost  of  broken-stone  roads  by  the  invention  of  the  rock-crusher 
and  the  road-roller,  there  is  little  excuse  for  the  construction 
of  the  cobblestone  pavement.  In  some  cities  it  has  been 
prohibited  by  law,  but  the  old  pavements  still  exist  in  such 
quantities  that  it  will  require  some  years  of  active  work  in 
repaving  before  it  is  entirely  extinct.  Practically  the  only 
paving  for  which  cobblestones  are  now  used  is  in  yards  and 
alleys,  and  for  gutters  and  crossings  of  unpaved  streets. 

Following  the  cobblestone  and  in  response  to  the  demand 
for  an  improvement  on  them,  came  what  has  always  been  known 
in  this  country  as  the  "  Belgian  block."  In  shape  it  was  a  trun- 
cated pyramid,  with  base  about  5  or  6  inches  square,  and  a 
depth  of  from  7  to  8  inches,  the  bottom  of  the  block  being 
of  dimensions  of  not  more  than  1  inch  different  from  the  top. 
This  was  an  improvement  on  the  cobblestone  and  when  well 
shaped  and  of  proper  material  made  a  very  good  pavement. 
It  was  introduced  into  New  York  and  vicinity  about  1850, 
and  it  soon  became  quite  popular. 

This  form  of  pavement  was  the  result  of  a  development  in 
Europe  from  the  early  pavements,  made  of  large  rectangular 
blocks.  These  had  several  square  fee£  of  top  surface  and 


STONE  BLOCK  PAVEMENTS 


315 


block 
pavement. 


were  laid  lengthwise  of  the  street,  but  as  traffic   increased,  it 

was   found   that   the  long  joints,  being  parallel  to 

the  direction  of  travel,  rapidly  wore  into  ruts  and  the     Belgian 

pavement  became  rough  and  uneven.     To  obviate 

this,  the  blocks  were    made    square  and  were  laid 

with  their  sides  at  an  angle  of  45  degrees  with  the  line  of  the 

street.     These  large  blocks  soon  proved  unsuitable  for  heavy 

traffic,  as  it  was  difficult  to  bed  them  so  that  they  would  keep 

their  place,  and  as  their  large  surface  did  not  afford  a  good 


FIG.  172.— Cobblestone 
Hammer. 


FIG.  173.— Stone  Paver's 
Hammer. 


FIG.  174.— Cobble-    FIG.  175.— Stone  block 
stone  Rammer.  Rammer. 


foothold  for  horses.  This  led  to  the  use  of  smaller  square 
blocks  with  their  edges  parallel  and  perpendicular  to  the  line 
of  the  street.  For  many  years  this  form  of  pavement  has  been 
common  in  the  cities  of  Europe,  the  blocks  usually  having  a 
top  surface  of  5  to  7  inches  square  and  a  depth  of  6  inches. 
The  first  use  of  this  form  of  pavement  was  in  Brussels,  Belgium. 
In  New  York  and  vicinity  it  has  been  laid  almost  entirely 
of  trap-rock  from  the  Palisades  of  New  Jersey.  This  rock  is 
hard  and  durable,  but  after  some  wear  becomes  smooth  and 
slippery.  On  account  of  its  being,  at  first,  made  of  this  trap- 
rock,  all  trap-rock  pavements  have  been  called  "  Belgian 


316 


THE  ART  OF  ROADMAKING 


pavements/'  but  when  made  of  the  oblong  blocks  similar  to 
those  of  the  ordinary  granite  they  have  been  called  in  dis- 
tinction, "  specification  Belgian."  This  is  a  complete  mis- 
nomer, as  the  name  refers  distinctly  to  the  shape  and  not  to  the 
character  of  the  material,  as  some  Belgian  pavements  have 
been  made  of  granite. 

The  objections  to  the  Belgian  block  are: 

1.  On  account  of  the  size  and  form  of  the  blocks  it  is  difficult 
to  keep  them  in  place. 

2.  The  blocks  are  of  such  size  and  form  as  to  give  horses  a 
poor  foothold. 

3.  The  blocks  being  square  there  is  always  a  considerable 


FIG.  176. — Cross-section  of  Stone-block  Pavement. 

length  of  joints  parallel  to  the  line  of  travel,  which  causes 
ruts  to  form  in  the  pavement. 

As  the  blocks  became  more  common,  deviations  were  al- 
lowed from  the  specifications,  with  the  result  that  the  blocks 
were  too  small  on  the  base  to  allow  a  solid  bearing.  Also 
under  traffic  they  soon  got  out  of  position,  and  in  consequence 
the  pavement  became  rough.  An  improvement  in  the  Bel- 
gian block  was  to  make  the  block  an  exact  cube.  Many 
European  cities  at  the  present  time  lay  blocks  of  that  shape. 

Just  as  the  Belgian  block  supplanted  the  cobblestone,  it 
has  itself  been  gradually  displaced  by  the  introduction  of 
rectangular  blocks  of  granite.  Blocks  of  com- 
Gramte  paratively  large  dimensions  were  at  first  employed, 
pavement,  being  merely  placed  in  rows  on  the  subsoil,  per- 
functorily rammed,  the  joints  filled  with  sand,  and 
the  street  thrown  open  to  traffic.  The  unequal  settlement 
of  the  blocks,  the  insufficiency  of  the  foothold,  and  the  diffi- 


STONE  BLOCK  PAVEMENTS  317 

culty  of  cleansing  them  led  to  the  gradual  development  of  the 
later  type  of  stone-block  pavements,  consisting  of  narrow 
rectangular  blocks  of  granite,  properly  proportioned,  laid  on 
an  unyielding  and  impervious  foundation,  with  the  joints 
between  the  blocks  filled  with  an  impermeable  cement.  This 
type  is  practically  a  return  to  the  s}rstem  of  the  Romans,  but 
with  blocks  of  lesser  dimensions  than  they  used. 

Experience  has  proved  that  this  type  of  pavement  is  the 
most  enduring  and  economical  for  roadways  subjected  to 
heavy  and  constant  traffic.  Its  advantages  are: 

1.  Adaptability  to  all  grades. 

2.  Suitable  for  all  classes  of  traffic. 

3.  Exceedingly  durable. 
4-  Mr  foothold. 

5.  Easily  kept  in  repair. 

6.  Yields  little  dust  or  mud. 

7.  Moderately  easy  to  clean. 
Its  defects  are: 

1.  Greasy  and  slippery  surface  when  damp. 

2.  Noisy.     The  constant  noise  of  the  traffic  over  it  is  an 

intolerable  nuisance  and  is  claimed  by  physicians  to 
be  injurious  to  the  nerves  and  health  of  persons  who 
live  or  do  business  near  it. 

3.  Wear   on   horses   resulting   from    the    continual   jarring 

produced  in  their  legs  and  hoofs. 

4.  Discomfort  to  persons  riding  over  it. 

5.  If  smooth-wearing   rocks  are  used,  the   surface  quickly 

becomes  slippery  and  unsafe. 

The  harder  and  more  durable  rocks  like  basalt  and  true 
granite  are  unsuitable,  as  they  have  the  fault  of  wearing  smooth 
when  subjected  to  heavy  traffic,  and  under  certain 
conditions  of  the  weather  they  become  greasy  and     j^e*  stone 
slippery.     The  less  durable  rocks,  such  as  syenite, 
and  the  harder  sandstones,  are  the  most  suitable;   they  do  not 
polish  and  afford  a  good  foothold  for  the  horses. 

The  size  of  the  blocks  has  varied  considerably,  and  a  great 
variety  of  forms  and  dimensions  are  to  be  found  in  all  cities. 
For  stability  a  certain  proportion  must  exist  between  the 


318  THE  ART  OF  ROADMAKING 

depth,    the   length,    and   the   breadth.     The  depth   must  be 

such  that  when  the  wheel  of  a  loaded  vehicle  passes 

Size  and       over  one  edge  of  its  upper  surface   it   will  not  tip 

f  .ap^s°         up,  otherwise  the  maintenance  of  a  uniform  surface 

is  impossible.     To  fulfill  this  requirement  it  is  not 

necessary  to  make  the  block  more  than  seven  inches  deep. 

The  maximum  width  of  the  blocks  is  controlled  by  the  size 
of  horses'  hoofs.  To  afford  good  foothold  to  horses  drawing- 
heavy  loads,  it  is  necessary  that  the  width  of  each  block 
measured  along  the  street  shall  be  the  least  possible  consistent 
with  stability.  It  is  desirable,  therefore,  that  the  width  of  a 
block  should  not  exceed  three  inches,  or  that  four  taken  at 
random  and  placed  side  by  side  will  not  measure  more  than 
fourteen  inches. 

The  length  measured  across  the  street  must  be  sufficient 
to  break  joints  properly,  for  two  or  more  joints  in  a  line  lead 
to  the  formation  of  grooves.  For  this  purpose  the  length  of 
the  block  should  be  not  less  than  nine  inches  nor  more  than 
twelve  inches. 

The  blocks  should  be  well  squared  and  must  not  taper  in  any 
direction,  and  both  sides  and  ends  should  be  free  from  irregular 
projections. 

The  blocks  should  be  laid  in  parallel  courses,  with  their 

longest   side    at   right   angles   to   the   axis   of   the 

Manner  of     street,  and  the  longitudinal  joints  broken  by  a  lap 

blocks  °^  a^  least  two  inches,   to  prevent  the  formation 

of  longitudinal   ruts,  which   would   happen   if   the 

blocks  were  laid  lengthwise. 

At  junctions  or  intersections  of  streets  the  blocks  should 
be  laid  diagonally  from  the  centre  to  prevent  the  traffic  crossing 
the  intersection  from  following  the  longitudinal  joints  and  thus 
forming  depressions  and  ruts,  and  affording  better  foothold  for 
horses  turning  the  corners. 

The  foundation  of  the  blocks  must  be  solid  and  unyielding, 
and  for  this,  hydraulic  cement  concrete  is  exten- 
tion11  sively  used.  The  thickness  must  be  regulated  ac- 

cording to  the  traffic,  but  should  not  be  less  than 
four  inches  and  need  not  be  more  than  nine  inches.  A  thick- 


STONE  BLOCK  PAVEMENTS  319 

ness  of  six  inches  will  sustain  a  traffic  of  600  tons  per  foot  of 
width. 

Between  the  surface  of  the  concrete  and  the  base  of  the 
blocks  there  is  placed  a  cushion-coat  formed  of  fine,  clean  and 
dry  sand,  which  readily  adjusts  itself  to  the  irregularities  of 
the  base  of  the  blocks  and  transfer  the  pressure  of  the  traffic 
uniformly  to  the  concrete  below. 

The  blocks  are  laid  stone  to  stone,  so  that  the  joint  may  be 
of  the  least  possible  width;    wide  joints  cause  increased  wear 
and  noise  and  do  not  increase  the  foothold.     The 
courses  are  commenced  on  each  side  and  worked    jj"*^8  the 
to\vard    the    middle,    and    the    last    stone    should 
fit  tightly. 

After  the  blocks  have  been  set  they  are  well  rammed  down, 
and  the  stones  which  sink  below  the  general  level  are  taken 
up  and  replaced  with  a  deeper  stone  or  brought  to  level  by 
increasing  the  sand-bedding. 

All  stone-block  pavements  depend  for  their  water-proof 
qualities  upon  the  character  of  the  joint-filling.  Joints  filled 
with  sand  and  gravel  are  of  course,  pervious,  while 

a  grout  of  lime  or  cement  mortar  does  not  make  a          J«.int" 

filling. 

permanently  water-tight  joint,  as  it  becomes  dis- 
integrated unoer  the  vibration  of  the  traffic.  An  impervious 
joint  can  only  be  made  by  employing  a  filling  made  from 
bituminous  or  asphaltic  material;  this  renders  the  pavement 
more  impervious  to  moisture,  makes  it  less  noisy,  and  adds 
considerably  to  its  strength. 

The  bituminous  materials  employed  are:  1.  The  tar  pro- 
duced in  the  manufacture  of  gas,  which,  when  redistilled,  is 
called  distillate,  and  is  numbered  according  to  its  density;  this 
material,  under  the  name  of  paving-pitch,  is  extensively  used 
both  alone  and  in  combination  with  other  bituminous  SUD- 
stances;  2.  Combinations  of  gas-  or  coal-tar  with  refined 
asphaltum;  3.  Mixtures  of  refined  asphaltum,  creosote,  and 
coal-tar. 

Stone  blocks  may  be  employed  on  all  practicable  grades, 
but  on  grades  exceeding  ten  per  cent,  cobblestones  afford  a 
better  foothold  than  blocks.  If  stone  blocks  are  used,  they 


320 


THE  ART  OF  ROADMAKING 


FIG.  177. — Filling  in  Stone-block  Pavement  with  Asphalt  Bitose  Filler. 


STONE  BLOCK  PAVEMENTS  321 

must  be  laid,  when  the  grade  exceeds  five  per  cent.,  with  a 

serrated  surface,  made  by  slightly  tilting  the  blocks 

on  their  bed   so   as  to  form  a   series   of   ledges  or    Pavements 

steps  against  which  the  horses'  feet  being  planted, 

a  secure   foothold   is   obtained.      Another   method 

consists  in  placing  between  the  rows  of  stones  a  course   of 

slate,  or  strips  of  creosoted  wood,  rather  less  than  one  inch 

in    thickness    and    about    an   inch   less   in   depth    than    the 

blocks;  or  the  blocks  may  be  spaced  about  one  inch  apart, 

and  the  joints   filled   with  a  grout   composed   of  gravel   and 

cement. 

The  average  life  or  durability  of  granite  blocks  under  heavy 


FIG.  178. — Arrangement  of  Stone  Blocks  on  Steep  Incline. 

traffic  may  be  taken  at  fifteen  years;   but  since  the  nature  of 
the  traffic,  the  state  of  cleanliness  and  other  con- 
ditions must  be  taken  into  account  when  inquiring     Durability 
into  the  durability,  it  follows  that  in  no  two  streets     blocks™ 
is  the  endurance  and  the  cost  the  same,  and  the 
difference  between  the  highest  and  the  lowest  period  of  en- 
durance and  amount  of  cost  is  very  considerable.     The  practice 
followed  in  European  cities  is  to  remove  the  worn  blocks, 
re-dress  them  and  re-lay  them  in  other  and  secondary  thorough- 
fares.    Thus  the  duration  of  life  of  the  blocks  may  be  doubled, 
or  more  than  doubled.     In  fact,  with  the  exception  of  the 
portion  worn  off  by  the  friction  of  the  traffic,  not  a  fragment 
of  granite  paving  may  be  said  to  be  lost.     After  passing  its 
first  years  in  a  leading  thoroughfare  it  goes  into  a  secondary 
thoroughfare  until  completely  worn  down  and  rounded,  and 


322  THE  ART  OF  ROADMAKING 

not  even  a  fragment  that  is  knocked  off  the  component  stones 
when  undergoing  the  operation  of  being  dressed  into  shape 
is  lost,  as  it  is  made  available  either  for  macadamizing  or  for 
concrete  to  form  the  foundation  of  other  pavements.  Granite 
can  only  be  said  to  be  worn  out  when  it  has  been  broken  up 
for  macadamizing  and  then  crushed  into  powder  by  the 
vehicles. 

Stones  from  different  quarries  and  even  from  the  same  quarry 
will  show  considerable  variation  in  the  amount  worn  away 
in  a  given  time  under  exactly  similar  conditions.  Therefore 
no  statement  of  wear  can  be  given  which  will  be  applicable 
to  all  varieties  of  stone. 


CHAPTER  XV 
BRICK    PAVEMENTS 

BRICK  pavements  consist  of  bricks  laid  on  edge  on  a 
suitable  foundation  of  concrete,  gravel,  sand,  or  wood.  Al- 
though brick  is  one  of  the  oldest  materials  used  for  paving, 
its  first  use  for  this  purpose  in  the  United  States  was  in 
Charleston,  W.  Va.,  about  1870.  Since  then  the  use  of  brick 
as  a  paving  material  has  steadily  increased,  and  in  localities 
with  moderate  traffic  it  has  given  satisfaction. 

The  advantages  of  brick  pavements  are: 

1.  Ease  of  traction. 

2.  Good  foothold  for  horses. 

3.  Not  disagreeably  noisy. 

4.  Yields  but  little  dust  and  mud. 

5.  Adapted  to  all  grades. 

6.  Easily  repaired. 

7.  Easily  cleaned. 

8.  But  slightly  absorbent. 

9.  Pleasing  to  the  eye. 

10.  Expeditiously  laid. 

11.  Durable  under  moderate  traffic. 

In  many  localities  brick  is  superior  to  wood  or  broken  stone, 
and  in  cities  and  towns  will  often  be  found  superior  to  stone 
blocks. 

The  principal  defects  of  brick  pavements  arise  from  (1)  lack 
of  uniformity  in  the  quality  of  the  bricks,  and  (2)  the  lia- 
bility of  incorporating  in  the  pavement  bricks  of  too  soft  or 
porous  structure,  which  crumble  under  the  action  of  traffic  or 
frost. 

The  employment  of  unsuitable  brick  may  be  Quality 
fostered  by  a  desire  to  help  a  local  industry  °* bnck 
without  due  regard  to  the  quality  of  the  local  clays  for 

323 


324 


THE  ART  OF  ROADMAKING 


the  manufacture  of  good  paving  brick.  A  paving  brick  is 
simply  a  brick  which,  through  careful  selection  of  material 
and  through  skillful  manufacture,  is  so  hard  and  tough  that 
it  will  resist  the  crushing  and  abrading  action  of  the 
traffic. 

The  qualities  essential  to  a  good  paving  brick  are  the  same 
as  for  any  other  paving  material,  viz.:  hardness,  toughness, 
and  ability  to  resist  the  disintegrating  effects  of  water  and 
frost.  These  qualities  are  not  obtained  by  "vitrifying"  the 
bricks,  as  is  commonly  supposed.  Vitrification  is  the  process 


FIG.  179. 

Brick  Paver's 

Hammer. 


FIG.  180. — Brick  Pavement  laid  on  Sand. 

of  converting  into  glass  by  fusion  or  the  action  of  heat,  and  adds 
nothing  to  the  strength,  but  really  defeats  the  object  for  which 
the  bricks  are  made.  The  required  qualities  are  imparted  to 
the  brick  by  a  process  of  annealing,  by  which  the  bricks  are 
burned  to  the  point  of  fusion,  then  the  heat  gradually  reduced 
until  the  kiln  is  cold.  This  process  produces  a  brick  of  uniform 
texture,  thoroughly  compact,  hard  and  tough,  but  if  the  cooling 
off  is  done  quickly,  it  will  produce  a  brittle  brick  that  will 
speedily  go  to  pieces  under  traffic. 

There  are  three  distinct  classes  of  clays  employed  in  the 
manufacture  of  paving  brick — surface  clays,  impure  fire  clays, 


BRICK  PAVEMENTS  325 

and    shales.     Surface  clays  are  almost  exclusively   used  for 
the  manufacture  of   building   bricks,  but  are   not 
ordinarily  suitable  for  making  paving  bricks,  since  it  Brick 

is  practically  impossible  to  burn  them  hard  enough 
without  their  losing  their  shape.  Pure  fire  clay  is  also  unsuit- 
able for  paving  brick  on  account  of  its  infusibility,  but  impure 
fire  clay  makes  a  fair  quality  of  paving  brick,  although  the  proc- 
ess is  expensive.  Most  paving  bricks  are  made  from  shale, 
an  impure,  hard,  laminated  clay  which  has  been  subjected  to 
great  earth  pressure,  and  which  is  widely  distributed. 

In  determining  the  value  of  a  brick  clay  the  following 
physical  properties  are  important  factors: 

1.  Plasticity. 

2.  Amount  of  water  required  to  make  a  plastic  mass. 

3.  Amount  of  shrinkage,  both  in  burning  and  m  drying. 

4.  Rapidity  of  drying  and  of  burning. 

5.  Temperature  of  incipient  and  complete  fusion. 

6.  Density  before  and  after  burning. 

7.  Strength  of  the  burned  brick. 

The  production  of  paving  brick  in  1894  was  restricted  within 
narrow  limits  in  Pennsylvania,  Ohio,  Indiana,  and  Illinois  on 
the   west,   which  produced  the   special  quality   of 
material  required  for  this  purpose,  differing  entirely      eglon  ° 
from  that  used  in  ordinary  building  bricks. 

There  are  now  a  number  of  places  outside  these  limits  where 
paving  bricks  are  produced  in  large  quantities,  one  of  the  large 
plants  being  on  the  Hudson  river  at  Catskill,  from  which  have 
been  furnished  bricks  for  pavements  in  many  cities  and  towns 
in  the  eastern  and  the  southern  states. 

In    the    manufacture    of    the    brick,    the    soft,  Manufacture 
homogeneous  clay  is  run  through  rollers,  to  crush  jjjri££j mg 
the  lumps ;  it  is  then  mixed  with  water  and  worked 
into  a  plastic  mass,  which  then  goes  to  the  brick  machine. 
Hard  clay  and  shales  are  usually  reduced  to  a  powder,  which 
is  screened  and  then  mixed  with  water.     The  more  thoroughly 
the  clay  is  worked,  or  tempered,  the  more  uniform  and  better 
will  be  the  brick. 

Paving  bricks  are  usually  made  by  the  "  stiff  mud  "  process, 


326  THE  ART  OF  ROADMAKING 

the  molding  being  done  by  an  auger  machine  which  forces  the 
tempered  clay  or  stiff  mud  through  a  die.  This  gives  a  con- 
tinuous bar  of  compressed  clay  which  passes  under  an  auto- 
matic machine  that  cuts  the  bar  into  bricks  of  the  desired 
size.  These  bricks  are  re-pressed  to  make  them  more 
symmetrical  in  form  and  of  better  appearance,  and  are  then 
placed  on  trucks  and  conveyed  to  the  dry-house.  Thorough 
drying  facilitates  the  burning  of  the  brick. 

The  process  of  burning  is  the  most  critical  in  the  manufac- 
ture of  paving  bricks.  They  are  usually  burned  in  down- 
draft  brick-ovens  having  fire  pockets,  or  furnaces,  built  in 
their  outer  walls.  The  bottoms  of  the  kilns  are  perforated 
to  allow  the  gases  to  pass  through  the  flues,  which  are  be- 
neath the  floor,  and  which  lead  to  the  chimney.  The  fire 
passes  up  from  the  furnaces  into  the  kilns,  then  down  through 
the  bricks  to  be  burned  to  the  flues,  and  thence  to  the  chimney. 
At  first  the  heat  is  applied  slowly  to  drive  off  the  water  without 
cracking  the  bricks;  this  low  heat  is  continued  until  the 
smoke  passing  off  shows  no  further  signs  of  steam,  after  whicli 
the  fires  are  gradually  increased  until  the  temperature  through- 
out the  kiln  is  sufficient  to  fuse  the  bricks.  This  tempera- 
ture is  for  shales,  from  1500°  to  2000°  F.,  and  for  impure 
fire-clays  from  1800°  to  2300°  F.  From  seven  to  ten  days\ 
are  required  to  raise  the  entire  kiln  to  this  temperature. 

After  the  burning  process  is  completed,  the  kiln  is  tightly 
closed  and  allowed  to  cool  slowly,  rendering  them  very  tougl\.\ 
This  process  requires  several  days;    it  is  often  completed  i» 
three  to  five  days,  when  seven  to  ten  days  would  materially^ 
improve  the  product  and  usually  would  be  worth  the  extra\ 
cost.     Slow  cooling  is  the  secret  of  toughness,  and  the  slower^ 
the  cooling  the  tougher  the  brick. 

Bricks  have  passed  through  much  the  same  process  that 
stone  and  wood  blocks  have  passed  through  in  being  stand- 
ardized as  to  size  and  shape.  Experience  has  shown  that 
with  the  proper  foundation  neither  odd  shapes,  grooves,  lugs, 
nor  other  devices  are  necessary,  and  that  the  most  economical 
and  desirable  size  for  paving  bricks  is  that  of  the  standard 
building  brick.  Bricks  of  this  size  can  be  made  more  cheaply, 


BRICK  PAVEMENTS  327 

burned  more  uniformly,  and  those  which   are  unsuitable  for 
paving  can  be  utilized  for  building  purposes,  which 
would  be  impracticable  with  odd  shapes.     The  im-       Size  and 
perfect  ones  of  odd  or  peculiar  shape  are  so  much        bricks 
waste   material,    and   the   cost   of   their   manufac- 
ture must  be  added  to  the  price  of  the  good  ones  in  order 
to    protect    the    manufacturer    from    loss.     Moreover,    with 
irregular  sizes  and  odd  shapes  it  would  be  necessary  for  the 
towns  employing  brick  pavements  to  keep  a  large  stock  of 
the  different  bricks  on  hand  to  make  repairs,  which  would  be 
expensive  and  troublesome. 
The  sizes  in  common  use  are: 

1.  The  "paving  brick/7  measuring  8^  x  2J  x  4  inches,  weigh- 

ing about  7  pounds  and  requiring  58  to  the  square 
yard. 

2.  The  "  paving  block,"  measuring  3x4x9  inches,  weigh- 

ing about  9^  pounds  and  requiring  45  to  the  square 
yard. 

Both  bricks  and  blocks  are  made  with  either  flat  sides  and 
square  edges  or  flat  sides  and  rounded  edges,  some  users 
claiming  that  the  rounded  edge  wears  better  than  the  square 
edge.  A  variation  from  the  flat  sides  is  made  by  grooves  and 
projections  formed  during  the  re-pressing,  the  object  of  which 
is  to  facilitate  the  introduction  of  the  joint  filling  and  to  in- 
crease its  holding  power.  The  grooves  are  formed  either  by 
having  the  name  of  the  maker  in  sunken  letters  or  one  or  more 
horizontal  grooves  on  sides  and  ends.  Some  makers  form 
both  horizontal  and  vertical  grooves;  horizontal  grooves  are 
by  some  considered  objectionable,  for  the  reason  that  the 
brick  is  liable  to  spall  or  fracture  down  to  the  groove.  The 
projections  are  formed  by  having  the  name  of  the  maker  in 
raised  letters  or  by  either  round  or  square  buttons.  The 
depth  of  the  grooves  and  height  of  the  projections  vary  with 
the  maker  from  one-eighth  to  three-sixteenths  inch. 

The  brick  should  be  reasonably  perfect  in  shape,  free  from 
marked  warping  or  distortion,  and  uniform  in  size,  so  as  to 
fit  closely  together  and  make  a  smooth  pavement. 

In  the  matter  of  testing,  it  is  always  important  to  have 


328 


THE  ART  OF  ROADMAKING 


Testing 
bricks. 


a  definite  method  of  testing  the  qualities  of  any  artificial 
material,  since  then  all  parties  may  know  exactly 
the  grade  called  for,  and  since  the  results  obtained 
by  different  observers  with  different  materials  may 
be  compared.  This  is  particularly  true  of  brick,  as  the  clays 
differ  greatly  in  quality  and  also  as  a  slight  variation  in  each 
step  of  the  manufacture  materially  affects  the  result.  The 


FIG.  181. — Grooved  Paving  Blocks. 

object  of  testing  paving  brick  is  (1)  to  determine  whether 
the  material  is  suitable  for  use  in  a  pavement,  and  (2)  to 
enable  comparisons  to  be  made  between  different  classes  of 
brick.  The  various  methods  of  inspecting  and  testing  paving 
brick,  together  with  the  objects  to  be  attained  by  these  methods, 
are  treated  fully  and  in  detail  in  Baker's  "Roads  and  Pave- 
ments." 

In  the  construction  of  brick,  as  of  other  pavements,  the 
foundation  must  first  be  considered.  Each  brick  should  have 
an  adequate  support  from  below,  as  otherwise  the  loaded 
wheels  will  force  it  downward  and  make  the  surface  uneven. 
Various  materials  may  be  used,  but  experience  has  shown 
that  the  best  foundation  is  a  bed  of  concrete.  On  this  a 
layer  of  sand  is  spread  to  secure  a  uniform  bearing  for  the 


BRICK  PAVEMENTS  329 

bricks.      The  sand    used   for    this    cushion    layer  should    be 
clean,  moderately  coarse  and  free  from    loam  and     ^ 
vegetable    matter,  and    from   pebbles    of   any  size     tion  of 
that  will  cause  the  bricks  to  set  unevenly.  pavement 

The  bricks  should  be  laid  on  edge,  as  closely  and  compactly 
as  possible,  in  straight  courses  across  the  street,  with  the 
length  of  the  bricks  at  right  angles  to  the  axis  of 
the  street.  At  street  intersections  and  junctions  Manner 
the  bricks  should  be  laid  diagonally — a  compro-  Bricks118 
mise  position  between  the  directions  of  the  travel 
on  the  two  streets.  Street  intersections  need  special  care  in 
construction,  since  they  are  exposed  to  the  traffic  of  two  streets. 
To  provide  for  the  expansion  of  the  pavement,  both  longi- 
tudinal and  transverse  expansion-joints  are  used;  the  first 
are  formed  by  placing  a  board  templet  seven-eighths  of  an 
inch  thick  against  the  curb  and  abutting  the  brick  thereto. 
The  transverse  joints  are  formed  at  intervals  varying  between 
25  and  50  feet,  by  placing  a  templet  or  building-lath  three- 
eighths  of  an  inch  thick  between  two  or  three  rows  of  brick. 
After  the  bricks  are  rammed  and  ready  for  grouting,  these 
templets  are  removed,  and  the  spaces  so  left  are  filled  with 
coal-tar  pitch  or  asphaltic  paving-cement.  After  25  or  30 
feet  of  the  pavement  is  laid,  every  part  of  it  should  be  rammed 
with  a  heavy  rammer,  a  plank  being  laid  on  the  surface  parallel 
to  the  curb  to  receive  the  blows  of  the  rammer,  or  a  steam- 
roller weighing  not  to  exceed  5  tons  may  be  used.  After  the 
ramming  Portland-cement  grout  should  be  poured  into  the 
joints  until  it  appears  on  the  surface,  then  the  whole  surface 
should  be  covered  with  a  layer  of  dry  sand  one-half  inch  deep. 

The  character  of  the  material  used  in  filling  the  joints  be- 
tween the  brick  has  considerable  influence  on  the  success  and 
durability  of  the  pavement.  Various  materials  have  been 
used,  as  sand,  coal-tar  pitch,  asphalt,  mixtures  of  coal-tar 
and  asphalt,  Portland  cement,  and  various  patented  fillers, 
and  there  is  much  difference  of  opinion  as  to  which  gives  the 
best  results.  The  office  of  a  " filler"  is  to  prevent  water  from 
reaching  the  foundation,  and  to  protect  the  edges  of  the  brick 
from  spalling  under  traffic.  In  order  to  meet  both  of  these 


OF    THE 

UNIVERSITY 


330 


THE  ART  OF  ROADMAKING 


FIG.  182. — Herring-bone  Pattern. 


FIG.  183. — Double  Diagonal  Pattern. 

Brick  Paving  at  Street  Intersection. 


BRICK  PAVEMENTS  331 

requirements  every  joint  must  be  filled  to  the  top  and  remain 
so,  wearing  clown  with  the  brick.  Sand  does  not  meet  these 
requirements,  as  it  soon  washes  out  and  leaves  the  edges  of 
the  brick  unprotected  and  consequently  much  more  liable  to 
be  chipped.  Coal-tar  and  the  mixtures  of  coal-tar  and  asphalt 
have  an  advantage  in  rendering  the  pavement  less  noisy  and 
in  cementing  together  any  breaks  that  may  occur  by  upheavals 
from  frost  or  other  causes;  but  unless  made  very  hard  they 
have  the  disadvantage  of  becoming  soft  in  hot  weather  and 
flowing  to  the  gutters  and  low  places  in  the  pavement,  there 
forming  a  black  and  unsightly  scale  and  leaving  the  high 
parts  unprotected.  The  joints  thus  deprived  of  their  filling 
become  the  receptacles  of  water,  mud,  and  ice  in  turn,  and  the 
edges  of  the  brick  are  quickly  broken  down. 

The  best  results  seem  to  be  obtained  by  using  a  high  grade 
of  Portland  cement  containing  the  smallest  amount  of  lime 
in  its  composition. 

Brick  has  been  used  for  upwards  of  a  hundred  years  in  the 
Netherlands,  and  pavements  laid  half  a  century  ago  are  still 
in  good  condition.  There  are  several  brick  pave- 
ments in  the  United  States  from  ten  to  eighteen  Durability. 
years  old  which  are  still  in  good  condition.  The 
general  experience  with  pavements  formed  of  suitable  brick, 
laid  on  an  unyielding  foundation,  with  the  joints  properly 
filled,  is  that  they  furnish  a  smooth  and  durable  surface,  well 
adapted  to  moderate  traffic.  Failures  of  the  earlier  pave- 
ments were  caused  by  defective  foundations,  and  the  use  of 
ordinary  building  bricks  of  the  locality. 

The  durability  of  the  bricks  seems  to  depend  on:  1.  The 
clay  from  which  they  are  made  being  practically  free  from 
lime;  2.  The  thorough  grinding  and  mixing  of  the  clay,  so 
as  to  have  no  lumps  in  the  bricks;  3.  The  bricks  being  thor- 
oughly annealed. 

The  amount  of  maintenance  required  by  a  brick  pavement 
depends  upon  the  quality  of  the  brick  and  the  character  of 
the  foundation.  With  good  bricks  and  concrete  foundation 
the  amount  will  be  small,  with  a  weak  foundation  and  inferior 
bricks  it  will  be  large. 


332 


THE  ART  OF  ROADMAKING 


FIG.  184. — Brick  at  Entrance  to  Union  Station,  laid  in  1893.     (Stone-block 
pavement  in  foreground.) 


FIG.  185.— Alley  Paved  with  Brick  in  1894.     Brick  Pavements,  St.  Louis, 

1901. 

(From  Judson's  "City  Roads  and  Pavements.1') 


BRICK  PAVEMENTS 


333 


The  successful  use  of  vitrified  brick  for  the  paving  of  streets 
brought  about  much  discussion  of  its  adaptability      Brick  for 
to  country  roads  in  sections  where  good  stone  for      country 
macadam  is  not  really  obtainable,  and  it  has  been      roads. 


FIG.  186.  —  Cross-section  of  Country  Road  with  Earth  Side  Road. 


used  for  this  purpose  in  various  parts  of  the   country  with 
success. 

In  making  a  brick  country  road  in  Ohio  *  the  foundation 
material  consisted  of  broken  vitrified  sewer  pipe,  broken  to 


FIG.  187. — Brick  Country  Road. 

pass  through  a  2J-inch  ring,  with  sufficient  finer  material  to  fill 
voids  after  rolling  and  to  prevent  the  sand  cushion  from  passing 
downward.  Upon  the  foundation,  and  between  the  curbing, 
a  layer  of  clean  sand  was  placed,  and  on  this  the  brick  paving 

*  Engineering  News,  Sept.  25,  1902. 


334  THE  ART  OF  ROADMAKING 

was  laid.     This  was  laid  on  edge  at  right  angles  to  the  center 
line  of  paving,  and  kept  in  even  straight  lines. 

The  brick  was  covered  with  fine  dry  sand,  well  broomed 


]      j>4        Bric/r--^  Sand-,  ,6ravel       **Ji      J 

F 

30 'Street  Section.  Curb  and  Drain 

u?  *  '  •  *S 

6" Concrete...       j 'Sand 'Cushion^         4"Brick,      \  |V 


— ^ ~   -.v--.:^ 

Allegheny    County   Road   Section 

FIG.  188. — Brick-paved  Street  and  Highway  with  Vitrified  Clay  Curbing. 

in,  sufficient  only  to  fill  the  interstices  or  joints.  The  surface 
was  then  rolled  and  evenly  covered  with  J  inch  of  clean  dry 
sand. 


CHAPTER   XVI 
WOOD   BLOCK   PAVEMENTS 

FOR  more  than  seventy  years,  wood  has  been  used  for 
street  paving,  with  little  success,  however,  at  the  beginning, 
owing  to  incomplete  knowledge  of  the  materials  and  wrong 
methods  in  their  use.  It  is  only  within  the  last  decade  that 
wooden  pavements  have  been  laid  with  any  great  degree  of 
success.  Wood  has  many  qualities  which  especially  adapt 
it  for  paving,  and,  with  a  better  knowledge  of  the  fitness  of 
woods  other  than  those  now  used,  and  of  the  effect  of  pre- 
servatives upon  durability,  it  is  almost  certain  that  its  use 
for  this  purpose  will  steadily  increase. 

For  many  years,  longleaf  pine  was  practically  the  only 
wood  used  for  creosoted  block  pavements  in  the  United 
States,  the  only  important  exception  being  in  Minneapolis, 
where  Norway  pine  and  tamarack  were  laid  in  1902  and 
have  proved  successful.  Longleaf  pine  has  advanced  in 
price  so  rapidly  as  to  make  its  use  for  paving  very  costly, 
and  as  the  United  States  has  a  large  variety  of  commercial 
woods,  the  Forest  Service  undertook  a  study  of  the  subject, 
with  the  object  of  finding  some  woods  cheaper  and  more 
abundant  than  longleaf  pine,  which  would  prove  suitable  for 
pavements. 

The  first  use  of  wood  for  paving  is  said  to  have  been  in 
Russia,   where  rude  blocks  were  laid  several  centuries   ago. 
Wood  was  introduced  into  New  York  City  in  1835-36 
and     in     London    in     1839.     Continental     Europe    Progress  of 

wood. 

was  slower  to  take  it  up.     Many  forms  of  wood    paving< 
pavements   have   been   built,    but   the   only   form 
now   in    actual    construction   is   that   of    chemically    treated 
blocks.     The  corduroy -roads  of  a  century  ago  are  now  past 
history   although  there   can  yet  be   found,   crossing  swamps 

335 


336  THE  ART  OF  ROADMAKING 

on  the  line  of  the  old  military  road  built  in  1812  across  the 
Adirondack  wilderness,  from  the  Mohawk  valley  at  Schenec- 
tady  to  Ogdensburg  on  the  St.  Lawrence,  and  to  Sackett's 
Harbor  on  Lake  Ontario,  sections  of  corduroy  road,  which 
are  still  as  sound  as  when  laid,  having  been  preserved  from 
decay  by  the  water  which  has  usually  covered  them,  although 
huge  forest  trees  have  meantime  grown  up  in  the  old  and 
abandoned  roadway  near  at  hand.* 

The  plank  roads  of  a  century  ago  are  nearly  gone,  with 
the  toll-gates  which  were  the  objects  of  their  beginning  and 
the  cause  of  their  ending;  though  it  is  of  interest  that  there 
are  still  two  plank  roads  leading  from  the  westward  into  the 
city  of  Albany,  N.-Y.,  having  five  toll-gates  on  ten  miles  of 
road;  but  these  relics  of  old  days  are  of  only  historic  interest, 
as  are  the  majority  of  the  many  patented  and  forgotten  forms 
of  wood  pavements  which  had  their  rise  and  fall  thirty  to 
forty  years  ago. 

At  that  time,  the  chief  consideration  seems  to  have  been 
the  form  of  block.  The  large  and  unequal  interstices  between 
the  round  blocks  then  commonly  used  permitted  the  edges 
to  wear  off  rapidly  into  a  corduroy  condition  which  was 
uncomfortable  to  the  traveler,  and  which  hindered  both 
drainage  and  cleaning,  thus  making  the  pavement  unsanitary 
and  hastening  its  decay.  It  was  to  remedy  this  that  many 
different  forms  of  blocks  were  devised  during  the  period 
between  1840  and  1870,  of  which  perhaps  the  most  con- 
spicuous was  the  "Nicholson,"  patented  in  1848  and  laid 
extensively  in  the  ten  years  following  the  civil  war.  This 
block  was  rectangular,  which  gave  equal  interstices;  but 
this  by  no  means  solved  the  problem,  and  results  were  no 
better  than  before.  Little  thought  was  given  to  the  kind  of 
wood  used,  and  as  soft  a  wood  as  white  pine  was  frequently 
laid.  The  blocks  were  neither  seasoned  nor  treated  with 
chemical  preservatives,  and  quickly  decayed.  Wide  joints 
permitted  water  to  get  under  the  pavement,  where  it  was 
absorbed  by  the  blocks,  with  the  result  that  they  swelled, 

*  "City  Roads  and  Pavements,"  by  William  Pierson  Judson. 


WOOD  BLOCK  PAVEMENTS  337 

so  that  the  pavement  often  heaved  from  its  foundation. 
Finally,  the  foundation  was  usually  of  untreated  planks, 
laid  directly  upon  earth,  so  that  they  soon  decayed,  while 
the  pavement  sank  into  ruts  and  holes. 

Round  blocks,  mostly  of  white  cedar,  were  extensively  laid 
in  the  Middle  West,  and  with  most  success  in  Chicago.  They 
made  neither  a  durable  pavement  nor  in  any  way 
a  satisfactory  one.  But  they  were  cheap  and  Woods 
served  a  good  purpose  in  tiding  fast-growing 
cities  over  a  critical  period.  There  have  also 
been  laid  in  various  cities  pavements  of  oak,  cypress,  white 
pine,  hemlock,  Washington  red  cedar,  cottonwood,  mesquite, 
Osage  orange,  redwood,  Douglas  fir,  and  tamarack.  In 
nearly  all  these  cases  the  blocks  were  untreated,  or  at  most 
dipped  or  boiled  for  a  short  time  in  tar,  asphalt,  or  other 
mixture  of  supposed  preservative  value,  and  they  failed  to 
give  satisfactory  results.  Untreated  American  red  gum  was 
tried  in  England,  and  for  a  time  raised  great  hopes,  but  it 
finally  proved  unsatisfactory. 

Some  species  of  eucalyptus,  especially  jarrah  and  karri, 
have  been  laid  extensively  in  England.*  In  London  these 
woods  have  shown  a  life  of  from  fifteen  to  twenty  years,  but 
continued  use  has  not  entirely  justified  the  hopes  first  enter- 
tained for  them.  Their  structure  is  too  dense  to  permit 
impregnation  with  chemical  antiseptics,  without  which  they 
absorb  water  and  swell.  They  wear  much  more  slippery 
than  most  native  woods,  and  they  are  not  immune  from 
decay,  though  because  of  certain  antiseptic  gum-resins  which 
they  contain  they  are  more  so  than  any  untreated  native 

*  Jarrah  (E.  marginata)  and  Karri  (E.  diversicolor)  are  very  dense 
and  hard  woods,  growing  plentifully  in  Western  Australia.  Jarrah  is 
bright  to  dull  red  in  color;  short  grained;  free  splitting,  breaking  with 
a  clean  fracture,  and  burns  with  a  black  ash.  When  seasoned,  it  has 
a  specific  gravity  of  1.01  and  it  absorbs  about  10  per  cent  of  moisture 
when  immersed  forty-eight  hours,  as  against  the  absorption  by  most 
soft  woods  of  20  to  25  per  cent.  Karri  is  very  similar  in  appearance  to 
jarrah  but  somewhat  lighter  in  color,  is  interlocked  in  the  grain  and  is 
difficult  to  split;  it  splinters  in  breaking  and  burns  with  a  white  ash. 
When  seasoned,  it  has  a  specific  gravity  of  1.12,  and  absorbs  about 
7  per  cent  of  water  when  immersed  forty-eight  hours. 


338 


THE  ART  OF  ROADMAKING 


This  machine  cuts  240,000  blocks  per  day.  The  upper  half  of  the  machine  has 
been  raised  in  order  to  show  the  circular  saws  and  the  planks  of  wood  entering  the 
machine. 

FIG.  189.— Machine  for  Cutting  Wood  Paving  Blocks. 


WOOD  BLOCK  PAVEMENTS 


339 


woods.  In  England,  however,  they  are  still  used.  Jarrah 
blocks  were  laid  on  Twentieth  street,  New  York  City,  in  1895, 
but  were  removed  in  1904.  The  cost  of  this  pavement  was 
about  $5.00  per  square  yard,  which  would  exclude  these 
woods  from  extensive  use  in  America  even  should  they  make 
a  better  pavement  than  our  best  creosoted  native  woods, 
which  is  not  likely. 

After  the  failure  of  untreated  native  woods,  attention  was 
turned  to  wood  preservatives.  For  the  treatment  of  wood 
paving,  the  tendency  has  been  to  narrow  down  to  the  use  of 


FIG.  190. — Method  of  Cutting  Planks  from  Logs. 

one  material,  the  dead  oil  of  coal-tar,  commonly  called  creosote, 
either  pure  or  in  mixture  with  resin,  pitch,  or  other  materials. 
Creosoted  southern  pine  paving  blocks  are  said  to  have  been 
laid  in  the  United  States  at  Galveston,  Tex.,  as  early  as  1873. 
This  pavement,  in  spite  of  being  laid  on  a  foundation  of  sand, 
gave  satisfactory  service  for  nearly  thirty  years,  and  was 
destroyed  only  by  the  great  flood  of  1900.  But  this  good 
beginning  was  not  at  once  followed  up,  and  only  within  the 
last  ten  years  has  the  matter  received  systematic  attention 
in  this  country. 

The  success  of  the  modern  wood  block  pavement  is  due  to 
several  things.     The  wood  is  carefully  selected,   both  as  to 


340  THE  ART  OF  ROADMAKING 

kind  and  quality;  it  is  cut  accurately  into  rectangular  blocks, 

is  put  through  seasoning  processes  and  is  preserved 

Qualities  of   frOm  decay  by  chemical  means.      Its   liability    to 

treated  wood  aksorption  of  water  and  the  consequent  expansion 
pavement. 

and    contraction    of    the    pavement    are    reduced 

to  a  minimum.  The  blocks  are  then  laid  with  the  grain 
vertical,  over  an  accurately  surfaced  cushion  on  a  solid 
foundation  of  cement-concrete.  They  are  close-jointed,  and, 
in  the  best  practice,  the  joints  are  made  water-proof.  The 
result  is  a  pavement  having  the  advantages  of: 

1.  Comparatively  good  foothold  for  horses. 

2.  Smoothness   and   resiliency,    offering   less   resistance   to 

traction  than  stone  and  slightly  more  than  asphalt. 

3.  Suitability  for  all  classes  of  traffic. 

4.  Adaptability  to  grades  up  to  five  per  cent. 

5.  Even  wear  and  moderate  durability. 

6.  Cleanliness,  yielding  no  mud  and  but  little  dust. 

7.  Moderate  first  cost. 

8.  Comparative  rioiselessness. 
Its  principal  disadvantages  are: 

1.  Slipperiness  under  certain  weather  conditions. 

2.  Difficulty    in    opening   to    gain    access    to    underground 

pipes,  and  the  necessity  of  removing  a  rather  large 
surface  for  this  purpose  and  of  leaving  it  for  some  time 
after  being  repaired  before  traffic  can  be  resumed  upon 
it. 

3.  In  spite  of  its  many  advantages  it  is  claimed  by  many 

to  be  unhealthy. 

The  opinions  of  engineers  of  a  number  of  American  cities 
as  to  the  qualities  of  treated  wood  block  in  comparison  with 
other  paving  materials,  obtained  by  the  Forest  Service  of  the 
U.  S.  Department  of  Agriculture,  have  already  been  presented 
in  tabulated  form  on  page  32.* 

The  cost  of  creosoted  wood  pavement  in  the  United  States 

*  In  the  course  of  this  inquiry  much  information  was  obtained  in 
relation  to  creosoted  wood  block  pavements,  which  has  been  published 
under  the  title  "Wood  Paving  in  the  United  States,"  by  C.  L.  Hill,  Forest 
Assistant,  Circular  141,  Forest  Service,  U.  S.  Department  of  Agriculture. 


WOOD  BLOCK  PAVEMENTS  341 

has  varied  from  $2.40  to  $3.50  per  superficial  square  yard  laid. 
As  shown  in  Table  IV  (page  32),  the  average  cost 
per  yard  for  all  cities  which  reported  was  $3.10. 
The  basis  of  judgment  upon  a  pavement  should  be  the  returns 
upon  its  total  cost  for  the  life  period,  considered  as  an  invest- 
ment. In  Europe  this  is  done,  but  in  the  United  States  the 
first  cost  is  in  most  cases  given  undue  weight.  For  a  pave- 
ment such  as  creosoted  wood,  the  first  cost  of  which  is  high, 
this  method  is  very  unfair  and  reduces  the  pavement's  total 
standing  much  below  its  service  value.  Table  IV  takes  into 
account  the  factors  of  pavement  value  more  systematically 
than  do  other  methods  used  in  this  country,  but  it  does  not 
provide  a  basis  of  investment  returns.  A  better  way  would  be 
to  express  the  cost  item  in  terms  of  total  annual  charge;  this 
would  take  into  account  the  factor  of  durability,  and  would 
remove  it  from  separate  listing  in  the  table.  The  result 
would  be  much  more  consistent  and  accurate. 

Disregarding  cost,  and  basing  the  comparison  upon  service 
qualities  only,  the  difference  in  favor  of  creosoted  wood  is 
materially   increased.     Wood   ranks   very   high   in 
every    quality    listed,    except     in    freedom    from 
slipperiness  and,  to  a  less  extent,  in  durability.     It  is  highest 
in  those   qualities  which   contribute  to   the   acceptability   of 
the  pavement. 

There  is  in  the  United  States  almost  no  wood  pavement 
of  the  modern  kind  which  has  yet  been  down  long  enough  to 
show  its  durability.     The  values  assigned  by  the 
engineers  to  durability  are,  therefore,  based  prin- 
cipally on  general  impressions  and  inference  from  European 
experience.     There  are,  however,  a  few  cases  in  the  United 
States  which  offer  pertinent  evidence. 

In  Baltimore,  Md.,  in  the  summer  of  1901,  there  were  laid 
several  adjacent  strips  of  experimental  pavements,  including 
sheet  asphalt,  creosoted  wood,  and  several  kinds  of  brick. 
After  five  years'  service,  and  after  passing  through  the  great 
fire,  the  wood  was  in  better  condition  than  any  of  the  others. 

On  Michigan  avenue,  Chicago,  is  a  creosoted  longleaf  pine 
pavement,  laid  in  the  year  1900.  Adjoining  it  an  area  of 


342  THE  ART  OF  ROADMAKING 

asphalt  block  was  laid  at  the  same  time.  In  1905  the  asphalt 
blocks  were  removed  and  replaced  with  wood.  In  the  five 
years  the  asphalt  had  worn  down  on  an  average  one  inch, 
but  very  unevenly,  so  that  ruts  had  formed  and  the  blocks 
were  badly  rounded.  The  wooden  blocks  during  this  time 
had  worn  off  only  one-eighth  of  an  inch,  and  the  surface, 
except  for  a  badly  constructed  gutter  at  one  point,  was  still 
perfectly  smooth  and  of  even  grade. 

In  1902  the  Metropolitan  Street  Railway  Company,  of 
New  York  City,  decided  to  experiment  with  creosoted  wooden 
blocks  for  paving  between  its  tracks.  A  small  area  of  long- 
leaf  pine  was  laid  on  Hudson  street,  the  wood  being  flanked 
at  either  end  by  granite,  the  material  hitherto  used.  At  the 
point  selected  there  is  a  very  heavy  trucking  traffic  from 
the  North  River  wharves,  and  the  stresses  on  the  pavement, 
where  the  trucks  run  with  one  wheel  just  outside  the  car 
rail,  are  so  great  that  the  granite  begins  to  show  a  rut  in  six 
months,  and  is  renewed  almost  annually.  At  the  end  of 
four  years  the  wood,  though  showing  a  heavy  rut,  was  still 
sound  and  in  position  and  good  for  at  least  one  more  year. 
The  granite  on  either  side  had  been  renewed  three  times  during 
the  four  years. 

These  few  examples  can  not  of  course  be  regarded  as  final 
as  there  have  been  instances  in  which  creosoted  blocks  have 
given  poor  results,  caused  principally  by  improper  preservative 
treatment  of  the  wood  or  faulty  construction  of  the  pavement. 
The  many  cases  of  successful  pavement  indicate  that  such 
errors  are  responsible  for  the  failures  which  have  occurred, 
and  that  wood  block  pavement,  properly  prepared  and  laid, 
should  be  credited  with  a  durability  greater  than  14  in  a 
scale  which  rates  asphalt  blocks  at  14  and  whose  standard 
is  granite  at  20,  as  in  Table  IV. 

Nor  is  this  conclusion  invalidated  by  the  fact  that  European 
wood  pavements,  as  compared  with  granite,  show  a  dura- 
bility relatively  less  than  this.  American  longleaf  pine  is 
a  harder,  denser  wood,  and  has  greater  resistance  than  the 
European  pine  used  for  paving.  While  wood  preservation 
has  in  general,  attained  a  greater  perfection  in  Europe  than 


WOOD  BLOCK  PAVEMENTS  343 

in  America,  yet  American  creosote  treatment  of  wood  paving 
blocks  is  more  thorough  than  the  European. 

Resistance  to  traction  and  freedom  from  slipperiness  are 
opposing  qualities,  so  that  gain  in  one  is  likely  to  be  made 
at  the  expense  of  the  other.  Table  IV  shows 
creosoted  wood  and  the  asphalts  equal  in  the 
matter  of  tractive  resistance,  while  on  the  score  of 
freedom  from  slipperiness,  wood  is  placed  below  both  of 
the  others.  This  is  hardly  consistent,  as  recent  experiments 
indicate  that  in  these  respects  American  sheet  asphalt  varies 
considerably  with  the  temperature.  In  cold  weather  it  is 
exceedingly  hard,  smooth,  and  slippery,  but  in  hot  weather 
its  softening  causes  it  to  cling  to  the  tires  and  increases  its 
tractive  resistance  to  a  point  greatly  beyond  that  of  wood. 

Of  two  neighboring  cities  in  which  the  conditions  affecting 
the  pavements  are  practically  the  same,  the  engineer  of  one 
believes  wood  to  be  more  slippery  than  asphalt,  while  the 
engineer  of  the  other  believes  asphalt  to  be  more  slippery 
than  wood.  This  is  but  an  example  of  the  difference  of 
opinion  which  exist  on  this  point,  due  in  large  measure  to 
the  variation  in  the  asphalt  under  different  conditions.  In 
both  tractive  resistance  and  slipperiness  wood  appears  to  be 
more  constant  than  sheet  asphalt.  In  hot  weather,  therefore, 
wood  is  likely  to  be  more  slippery  than  asphalt,  while  in  cold 
weather  it  is  likely  to  be  less  slippery.  Wood  and  asphalt 
are  both  most  slippery  when  slightly  wet.  Between  different 
kinds  of  wood  there  may  also  develop  considerable  difference 
in  slipperiness.  Experience  has  shown  that  Norway  pine 
wears  much  less  slippery  than  longleaf. 

The  maximum  gradient  recommended  by  the  majority  of 
engineers  for  either  pavement  is  from  two  to  five  per  cent, 
according  to  the  conditions  of  climate  and  traffic. 

The  problems  to  be  met  in  wood  paving  are  (1)  problems 
peculiar  to  wood  and  wooden  pavements,  and  (2) 
problems    of   construction   common    to   all    pave-    QualitY  °* 
ments.     One  of  the  drawbacks  in  the  use  of  wood    for  paving. 
for  paving   has  been  a  lack  of  knowledge  of  the 
wood  itself.     For  example,  sapwood  has  always  been  thought 


344  THE  ART  OF  ROADMAKING 

to  be  both  weaker  and  more  subject  to  decay  than  heartwood. 
It  is  rigidly  excluded  from  most  wood  paving  specifications, 
and  all-heart  blocks  demanded.  The  inclusion  of  sapwood 
undoubtedly  caused  the  untreated  blocks  of  former  years 
to  wear  unevenly  and  to  decay  quickly.  But  the  preservative 
treatment  now  applied  provides  against  this  decay.  Recent 
tests  show  that  under  equal  conditions  of  moisture  content , 
the  sapwood  of  many  species  is  as  strong  as  the  heartwood. 
It  is  usually  less  strong  because  wood  is  rarely  used  under 
conditions  where  the  moisture  content  of  the  sapwood  is  as 
low  as  that  of  the  heartwood.  Preservative  treatment,  with 
proper  previous  seasoning,  reduces  the  moisture  content  of 
each  to  an  approximately  even  minimum,  and  the  heavy 
charge  of  oil  now  customary  in  American  wood  paving  treat- 
ment prevents  subsequent  absorption  of  moisture,  beyond 
a  small  per  cent.  After  five  years'  service,  there  is  no  dis- 
cernable  difference  in  wear  between  the  heart  and  the  sap 
portions  of  unseparated  Norway  pine  blocks  laid  in  Minneapolis. 
A  wood  pavement  fails  through  wear  and  decay,  and  many 
methods  have  been  invented  to  prevent  the  decay  arid  increase 
the  durability  of  the  timber.  Timber  thus  treated 
Wood  is  usec[  for  piles?  railroad  ties,  and  other  purposes, 

methods!8  as  we^  as  ^or  Pavmg  blocks.  Experiments  in  the 
preservative  treatment  of  wood  date  back,  as  far  as  is 
known,  to  1657,  when  Glauber  recommended  treating  wood 
with  tar.  Since  that  time  an  almost  endless  list  of  substances 
has  been  experimented  with,  but  the  methods  that  have 
stood  the  test  of  time  and  are  at  present  in  use,  consist  of 
injecting  different  kinds  of  antiseptics  into  the  pores  of  the 
wood. 

The  results  to  be  obtained  by  preservative  treatment  for 
wood  paving,  are: 

1.  Preservation  from  decay. 

2.  Mechanical  filling  of  the  pores,  to  prevent  the  absorption 

of  fluids,  which  further  accomplishes: 

a.  Elimination  of  expansion, 

b.  Increase  of  resistance  to  wear, 

c.  Maintenance  of  sanitary  value. 


WOOD  BLOCK  PAVEMENTS  345 

The  methods  of  treatment  best  known  are  those  called: 

"Kyanizing,"  using  ^'corrosive  sublimate, 

"Burnettizing/7  using  a  solution  of  chloride  of  zinc, 

"  Boucherizing,"  using  sulphate  of  copper, 

"  Creosoting,"  using  creosote  oil,  which  is  the  method  most 
used  in  the  United  States.' 

Creosote  oil  seems  to  meet  the  requirements  better  than 
any  other  preservative  commonly  used.  The  other  pre- 
servatives are  mostly  water  solutions,  which  are  easily  leached 
out  of  the  wood  and  thus  lose  their  preservative  effect.  More- 
over, being  themselves  largely  composed  of  water,  they  do 
not  prevent  expansion  in  the  blocks,  do  not  increase  their 
resistance  to  wear,  and  do  not  maintain  them  in  a  sanitary 
condition. 

Creosoting  has  generally  been  supposed  to  weaken  timber. 
The  results  of  experiments  conducted  by  the  Forest  Service 
indicate,    however,    that    the    creosote    itself    does 
not  lessen  the  strength  of  timber,   but  that  this 
result   in   practice  has  been  due  chiefly  to  certain    methods 
used  in  the  impregnation. 

The  Rush  Street  bridge  in  Chicago,  111.,  is  said  to  carry 
a  traffic  as  heavy  as  any  in  the  city.  It  has  two  20-foot  road- 
ways, which  were  paved  in  1899,  one  with  creosoted  longleaf 
pine  blocks,  the  other  with  uncreosoted  blocks.  The  creosoted 
pavement,  after  a  service  of  seven  years,  was  still  in  good 
condition  and  was  expected  by  the  chief  engineer  to  last 
several  years  more,  while  the  uncreosoted  pavement  had  to 
be  renewed  in  1902. 

The  explanation  of  these  facts  lies  in  the  antiseptic  qualities 
of  the  creosote  and  its  physical  action  in  filling  the  pores  of 
the  wood  and  decreasing  its  absorption  of  water.  Every 
pavement  is  wet  a  large  part  of  the  time,  and  wood,  when 
saturated  with  water,  has  generally  less  than  40  per  cent  of 
its  kiln-dry  strength.  The  creosoting  treatment,  by  lessening 
the  absorption  of  water,  maintains  the  strength  at  much 
nearer  the  dry-wood  value,  and  thereby  increases  the  actual 
service  strength. 

This  action  is  most  effective  only  when  the  wood  is  well 


346  THE  ART  OF  ROADMAKING 

seasoned  before  being  creosoted.  In  the  United  States  most 
creosoters  attempt  to  dry  the  wood  by  applying  steam  and 
vacuum.  Recent  experiments  have  shown  that  wood  will, 
except  when  very  green,  weigh  more  after  such  treatment 
than  before.  That  is,  by  this  process,  it  will  take  up  moisture 
rather  than  lose  it,  which  would  destroy  any  possible  gain  in 
strength  through  the  creosote  treatment.  Not  only  is  the 
steaming  in  most  cases  valueless,  but  if  carried  too  far,  as  it 
often  is,  it  seriously  injures  the  wood.  Natural  seasoning, 
which  in  Europe  is  used  almost  entirely,  would  certainly 
contribute  to  increased  excellence  of  results  in  the  United 
States. 

The  common  opinion  among  engineers  in  regard  to  the 
creosoting  of  wooden  pavements  is  expressed  by  a  prominent 
paving  engineer,  who  says: 

"For  wood  paving  creosoting  is  only  of  contingent  value. 
If  the  traffic  is  heavy  enough  to  wear  out  the  pavement  before 
it  decays,  which  it  will  do  on  most  city  streets,  it  is  a  waste 
of  time  and  money  to  creosote  the  blocks.  Creosoting  is  only 
economically  desirable,  therefore,  when  the  traffic  is  so  light 
that  decay  will  reduce  the  block  before  it  fails  from  wear." 

This  would  be  true  if  creosoting  treatment  had  no  effect 
on  wood  pavements  other  than  the  preservation  of  the  wood 
from  decay.  But  creosoting  effects,  through  the  increased 
service  strength  of  the  blocks,  an  additional  and  quite  different 
gain.  It  is  believed  that  there  is  already  enough  evidence, 
such  as  that  offered  by  the  Rush  Street  Bridge,  to  overthrow 
the  traditional  doctrine  of  the  limited  value  of  creosote  pre- 
servative treatment  for  wood  paving. 

Creosote  is  an  oil  of  tar  from  which  the  ammonia  has  been 
expelled.  Its  effect  on  the  wood  is  to  coagulate  the  albumen 
and  thereby  to  prevent  its  decomposition,  and  also  to  fill 
the  pores  of  the  wood  with  a  bituminous  substance  which 
excludes  both  air  and  moisture,  and  which  is  obnoxious  to 
the  lower  forms  of  animal  and  vegetable  life. 

In  the  United  States,  the  timber  for  paving  purposes  is  im- 
pregnated by  the  vacuum-pressure  method.  Closed  cylinders, 
usually  about  six  feet  in  diameter  by  about  100  feet  in 


WOOD  BLOCK  PAVEMENTS  347 

length,  are  used.     The  amount  of  oil  usually  injected  into  the 
wood  is  sixteen  pounds  per  cubic  foot,  though  in 
some  cases  it  reaches  twenty-two  pounds.     To  many     Impregna- 
engineers  this  has  seemed  an  unusually  large  amount,    t|^ber 
constituting    an   item   of  expense   in   the   already 
high  cost  of  wood  paving  which  might  profitably  be  reduced. 
But  the  necessity  for  the  prevention  of  moisture  absorption 
under  conditions  more  exacting  than  those  in  which  almost 
any  other  creosoted  wood  product  is  subjected,  makes  imper- 
ative the  impregnation  of  wood  paving  blocks  with  an  amount 
of  oil  per  cubic  foot  greater  than  that  ordinarily  given  to 
railroad  ties  or  construction  timbers.     The  tendency  is  toward 
heavier  charges  than  the  reverse,  to  secure  for  wood  pave- 
ment a  service  so  greatly  enhanced  as  to  yield  better  returns 
upon  the  investment,  even  at  the  higher  cost. 

In  Paris  the  blocks  are  usually  impregnated  by  merely 
soaking  for  a  short  period  in  an  open  tank,  and  the  amount 
of  oil  injected  per  cubic  foot  is  small.  The  life  of  Paris  pave- 
ment so  treated  is  from  six  to  fourteen  years  only,  according 
to  the  traffic;  and,  because  of  the  small  impregnation,  expan- 
sion in  the  pavements  is  large  and  calls  for  the  laying  of 
longitudinal  courses  of  blocks  at  the  curbs,  which  are  removed 
as  it  becomes  necessary.  The  vacuum-pressure  method  for 
the  treatment  of  wood  paving  blocks,  is  of  comparative  recent 
introduction.  This  is  the  reason  for  the  statement  that 
American  creosote  treatment  of  wood  paving  is  superior  to 
that  of  Europe.  The  excellence  of  European  wood  pavements, 
despite  this  defect,  is  largely  due  to  better  construction, 
maintenance  and  repair. 

The  creosote  as  ordinarily  used  is  an  effective  preservative 
in  itself,  but  it  tends  to  form  an  emulsion  with  water,  and  is 
in  time  washed  out  by  rains,  and  it  also  tends  to  evaporate 
half  to  three-fourths  on  exposure  to  the  sun  and  the  weather. 
To  avoid  these  defects  has  been  the  object  of  two  recent 
modifications  of  the  treatment;  one  called  the  "kreodone- 
creosote,"  and  the  other  the  "  creo-resinate "  process. 

This  consists  in  impregnating  the  seasoned  selected  blocks 
under  pressure  with  ten  pounds  per  cubic  foot  of  an  oil  derived 


348 


THE  ART  OF  ROADMAKING 


from  creosote  oil,  possessing  the  original  preservative  proper 
ties  with  a  longer  endurance,  and  also  having  the 

Zreodone-  effect  of  forming  a  varnish-like  film  or  coating 
on  the  outer  surface  of  the  wood,  protecting  it 
from  the  elements.  The  seasoned  blocks  are 

sterilized  by  subjecting  them  to  dry  heat  of  240°  Fahr.,  for 


creosote 
process 


Concrete  base  In  progre^i.  Ten-ton  roller.  Completed  pavement. 

FIG.   191. — Kreodone-Creosote  Wood-block  Pavement,   Meridian  Street, 
Indianapolis,  in  Progress  of  Construction. 

(From  Judson's  "  City  Roads  and  Pavements  ") 

eight  hours.  The  kreodone-oil  is  then  forced  into  the  fibers 
of  the  wood,  under  a  pressure  of  seventy  pounds  per  square 
inch  maintained  for  two  or  three  hours,  or  until  twelve  pounds 
have  been  absorbed  by  each  cubit  foot  of  the  wood. 

The   special   features   of  this   process   are   the   preliminary 
treatment  in  dry  heat  to  kill  the  germs  of  decay,  and  the 


WOOD  BLOCK  PAVEMENTS  349 

mixing  with  the  creosote  of  50  per  cent  of  melted  rosin  which 
is  forced  into  the  fibers  with  the  creosote,  where  it 
solidifies  and  seals  the  pores  of  the  wood  and  pre-        Cre°- 
vents  the  evaporation  of  the  creosote  or  its  displace-         process** 
ment  by  water,  which  can  find  no  entrance,  so  that 
the  pavement  does  not  swell  and  heave  when  wet. 

It  is  claimed  that  this  process  increases  the  density  of  the 
wood  and  also  its  resistance  to  impact  and  abrasion  over 
either  untreated  or  creosoted  wood.  It  is  further  claimed 
that  the  more  porous  blocks  take  up  more  of  the  creo-resinate 
mixture  than  the  denser  ones,  and  consequently  increase 
in  density  and  strength  to  a  greater  degree,  the  process  thus 
making  the  blocks  more  uniform  in  quality. 

For  the  most  satisfactory  service,  wood-block  pavement 
requires  a  concrete  foundation.  This  is  usually  made  from 
5  to  6  inches  thick,  although  some  engineers  reduce 
it  to  4  inches  on  lightly  traveled  residence  streets.  ^  cushion 
As  a  top  cushion  for  the  foundation  either  Portland 
cement  mortar  or  sand  is  used,  the  former  being  considered 
the  better.  The  bearing  for  the  blocks  is  permanent,  and,  if 
carefully  surface-trued,  can  be  made  as  even  as  desired;  and 
if  the  grout  is  mixed  slightly  damp  and  the  blocks  laid  in 
it  immediately,  it  provides  equally  as  good  a  "compensation 
for  minor  inequalities  in  the  height  of  the  blocks  as  sand  does. 
If  tar  can  be  used,  a  better  method  of  accomplishing  the  same 
object  is  to  mix  the  grout  in  the  usual  way  and  let  it  thor- 
oughly set,  after  which  a  coating  of  tar  should  be  applied 
and  the  blocks  bedded  in  it.  This  is  the  method  oftenest  used 
in  Europe.  Sand  makes  a  satisfactory  cushion  where  the 
slope  is  negligible  and  the  foundation  is  solid.  It  is  some- 
times preferred  on  the  ground  of  greater  elasticity  and  power 
of  accommodation,  and  it  has  the  merit  of  being  cheaper 
than  cement.  On  a  gradient,  however,  if  water,  by  any 
possibility,  gets  under  the  blocks,  it  is  likely  to  carry  the  sand 
to  the  bottom  of  the  slope  and  seriously  derange  the  pave- 
ment. On  bridges,  also,  if  there  is  much  crown  on  the  road- 
way, the  vibration  of  the  structure  is  likely  to  shift  the  sand 
from  the  center  of  the  crown  toward  the  gutter.  For  bridges 


350 


THE  ART  OF  ROADMAKING 


WOOD  BLOCK  PAVEMENTS  351 

the  usual  practice  is  to  lay  the  blocks  directly  on  carefully 
creosoted  planking. 

The  blocks  should  be  rectangular,  3  inches  wide,  4  to  6 
inches  deep  and  9  inches  long.  They  should  be  cut  from 
sound  timber,  free  from  sap  wood,  and  should  be 
rigidly  inspected,  especially  as  to  imperfections 
of  sawing,  as  to  knot-holes,  decay,  or  defective  corners  or 
edges,  as  to  squareness  of  the  angles,  and  as  to  thoroughness 
of  impregnation.  Voids  due  to  imperfections  in  any  of  these 
respects  often  can  not  be  properly  filled  by  the  joint  filler, 
and  are  very  detrimental  to  the  pavement.  In  European 
practice  no  variation  greater  than  one-sixteenth  inch  in  any 
dimension  of  the  blocks,  and  no  measurable  variation  in  the 
depth,  are  allowed.  There  the  blocks  are  also  required  to 
be  kept  carefully  protected  from  sun  and  weather  after 
treatment  and  until  they  are  laid.  Deterioration  from 
checking,  which  in  America  is  often  considerable,  is  thus 
prevented. 

Exclusion  of  second  growth  material  from  wood-paving 
specifications  is  immaterial,  except  in  so  far  as  young  trees 
contain  a  greater  proportion  of  sapwood  than  older  trees; 
and,  since  sapwood  is  separately  provided  for  in  most  cases, 
the  specification  prohibiting  second-growth  timber  could 
well  be  abandoned.  Sapwood  is  entirely  excluded  by  most 
wood-paving  specifications.  Under  existing  market  condi- 
tions, however,  it  is  quite  impossible  to  obtain  strictly  all- 
heart  southern  pine  such  as  the  specifications  demand.  The 
true  longleaf  pine  *  has  usually  so  narrow  a  sapwood  that  it 
could  be  neglected  without  danger  to  the  life  of  the  pavement. 
In  loblolly  pine  the  sapwood  is  often  very  wide;  but  this 
is  one  of  the  species  for  which  it  has  been' proved  that  the' 

*  The  terms  "longleaf"  and  "shortleaf"  pine  are  descriptive  of 
qualities  of  Southern  yellow  pine,  rather  than  of  botanical  species.  Thus, 
"shortleaf  pine"  would  cover  such  species  as  are  now  known  as  North 
Carolina  pine,  loblolly  pine  and  shortleaf  pine  "Longleaf  pine"  is 
descriptive  of  quality,  and  if  Cuban,  shortleaf,  or  loblolly  pine  is  grown 
under  such  conditions  that  it  produces  a  large  percentage  of  hard  summer 
wood,  so  as  to  be  equivalent  to  the  wood  produced  by  the  true  longleaf, 
it  would  be  covered  by  the  term  "Longleaf  Pine." 


352 


THE  ART  OF  ROADMAKING 


sap  wood  under  equal  conditions  of  moisture  content  is  as 
strong  as  the  heart  wood.  Therefore,  when  effective  season- 
ing of  paving  material  can  be  assured  before  the  creosote 
treatment,  the  prohibition  of  sapwood  in  southern  pine 
material  is  needless,  and  might  well  be  omitted  from  specifica- 
tions. 

A  more  pertinent  specification  would  be  one  excluding 
fast-grown  timber  in  pine  paving-block  stock — say  all  showing 
less  than  eight  rings  to  the  inch — since  it  is  the  porous  wood 
resulting  from  fast  growth,  rather  than  the  presence  of  sap- 
wood,  which  unfits  timber  for  this  use. 

The  angle  at  which  the  courses  are  laid  in  wood  pavement 
is  a  matter  of  some  importance.  The  most  obvious  angle 


90* 
NO    JOINT 


ONE.   JOINT 


•45* 
TWO   JOINTS 


.-CURB 
•'   f JOINT 

L.ON6ITUOINAL. 

COURSE 
'••JOINT 
LONGITUDINAL 
COunst 


BODY  COUftSU 


Angle  of 
courses. 


FIG.  193. — Different  Angles  used  in  Laying  Pavement. 

is  that  of  90°  with  the  curb,  which  takes  the  courses  straight 
across  the  street.  Probably  the  greater  part  of  the  wood- 
block pavement  in  the  United  States  is  so  laid. 
But  this  angle  permits  the  calks  of  horses'  shoes  to 
strike  in  a  direct  line  with  the  joints,  and  subjects 
the  pavement  to  a  wear  and  tear  which  may  largely  be 
avoided  by  laying  the  courses  at  an  oblique  angle.  Moreover, 
if  expansion  occurs,  transverse  as  well  as  lateral  expansion 
joints  are  necessary  to  provide  against  it,  and  transverse 
joints  of  this  character  in  wood  pavement  are  always  un- 
desirable. With  the  courses  laid  at  an  oblique  angle,  the 
thrust  of  the  pavement  in  case  of  expansion  will  impinge  in 
both  directions  upon  the  curb,  and  the  transverse  expansion 
joint  may  be  entirely  dispensed  with. 

The   oblique   angle   which   most   naturally   suggested   itself 


WOOD  BLOCK  PAVEMENTS  353 

was  45°,  and  a  large  amount  of  pavement  has  been  so  laid. 
There  has,  however,  developed  an  objection  to  this  angle. 
Transverse  expansion  in  wood  takes  place  in  two  directions, 
tangentially  to  the  rings  of  annual  growth,  and  radially  to 
them.  Of  these  the  transverse  expansion  is  greater  than  the 
radial.  As  will  be  seen  from  the  accompanying  diagram  of 
the  common  method  of  sawing  lumber,  a  majority  of  blocks 
have  their  long  axes  in  a  plane  tangent  to  the  annual  rings 
of  the  wood,  or  at  least  nearer  to  that  plane  than  to  the  radial. 
Therefore  the  force  due  to  tangential  expansion  will  be 
exerted  chiefly  in  the  direction  of  the  courses  in  the  pavement, 
and  the  lesser  or  radial  force  will  be  exerted  at  right  angles 
to  that  direction.  The  angle  of  45°  does  not  compensate 
the  differential  expansions  in  the  wood,  and  in  uncreosoted 
or  poorly  creosoted  pavements  twisting  strains  have  devel- 
oped. 

The  angle  between  45  and  90°  from  the  curb  has  therefore 
been  bisected  by  some  engineers,  making  the  angle  with  the 
curb  consequently  67^°.  This  solution  of  the  problem  was 
an  entirely  empirical  one,  but  it  seems  to  avoid  the  difficulties 
experienced  with  the  previous  angle. 

All  untreated  wood  blocks  absorb  water  and  expand  to 
a  considerable  extent,  and  treated  blocks  expand  appreciably. 
Unless  this  expansion  is  provided  for  it  is  likely  to 
disturb  the  curbs  or  lift  the  blocks  from  their 
foundation.  Transverse  expansion  joints  are  alto- 
gether bad.  The  objection  is  the  same  as  that  against  wide 
body  joints,  that  the  filler  wears  away  faster  than  the  blocks, 
leaving  a  depression  which  permits  the  edges  of  the  blocks 
to  wear  off  and  destroys  the  smoothness  of  the  pavement. 
Expansion  joints  should  be  longitudinal  at  the  curb,  with 
a  longitudinal  course  of  blocks  between  the  expansion  joint 
and  the  body  of  the  pavement,  and  between  each  expansion 
joint,  if  more  than  one  is  used.  The  most  satisfactory  results 
have  been  obtained  by  leaving  the  expansion  joint  open  for 
a  few  days,  when  it  may  be  filled  with  sand,  or  if  pitch  is 
used  to  fill  the  body  joints,  with  sand  up  to  within  one-half 
inch  of  the  surface,  and  the  remainder  with  pitch. 


354 


THE  ART  OF  ROADMAKING 


The  customary  width  of  this  joint  is  from  1J  to  2  inches  on 
each  side  of  a  60-ft.  roadway,  though  in  some  places  3  inches 
is.  allowed,  and  this  is  filled  up  with  either  a  hot  mixture  of 
pitch  and  creosote  oil,  sand,  or  clay. 

Considerable  creosoted  block  pavement  in  the  United 
States  has  been  laid  without  any  expansion  joints,  and  where 
the  creosoting  of  the  blocks,  as  well  as  the  laying  of  the 
pavement,  has  been  well  done,  little  serious  trouble  has 
been  experienced;  but  it  is  safer  to  provide  expansion 
joints. 

There  is  some  uncertainty  among  engineers  as  to  the  best 
joint  filler  for  wood  pavement.  One  prominent  engineer 
gives  it  as  his  opinion  that  if  the  traffic  is  heavy,  so  that 


FIG.  194. — Cross-section  showing  Joint  Filling. 

the  joints  between  the  blocks  will  be  speedily  obliterated, 
a  sand  joint  may  be  used  as  well  as  any  other,  and 
it  is  considerably  cheaper  than  the  others.  But 
if  the  traffic  is  not  heavy  enough  to  obliterate  the  joints,  sand 
permits  the  ingress  of  water,  and  gradually  works  down  and 
leaves  a  space  to  be  filled  with  debris,  which  lowers  the  sanitary 
value  of  the  pavement.  Cement  mortar  as  a  filler  is  water- 
proof at  first,  but  it  soon  crumbles  and  becomes  then  no 
better  than  sand.  Besides,  it  is  too  inelastic  and  increases 
the  noise  from  the  pavement. 

Except  under  heavy  traffic,  therefore,  some  substance  like 
coal-tar  pitch  is  preferable.  But  pitch  has  this  disadvantage 
—that  a  grade  which  will  not  crack  under  the  cold  of  winter 
is  likely  to  become  soft  and  sticky  in  the  heat  of  summer. 


WOOD  BLOCK  PAVEMENTS  355 

Care  is  necessary  to  select  a  quality  which  shall  avoid  these 
difficulties.  There  are  some  proprietary  preparations  on 
the  market  which  offer  specific  advantages  as  fillers,  since 
their  range  of  stability  is  greater  than  that  of  pitch,  so  that 
they  become  neither  brittle  nor  sticky,  at  least  under  natural 
conditions  in  a  temperate  climate.  To  fill  the  joints  effectively, 
pitch  should  be  heated  to  about  300°  F.  when  applied,  so  as 
to  insure  perfect  fluidity. 

The  top  dressing  for  wood  pavement  is  usually  of  screened, 
sharp  sand  or  of  finely  crushed  stone,  about  one-half  inch  in 
thickness.     This  is  allowed  to  remain  on  the  pave- 
ment about  two  weeks,  or  longer  when  convenient. 
The  top  dressing  benefits  wood  pavement  in  several 
ways.    A  certain  amount  is  ground  into  the  surface  of  the  blocks 
and  both  increases  their  resistance  to  abrasion  and  reduces 
slipperiness.     If  sand  has  been  used  for  a  joint  filler  the  sur- 
face sand  keeps  the  joints  filled  as  they  settle,  and  if  the  joint 
filler  is  pitch  the  sand  takes  up  any  surplus  pitch  from  the 
surface  of  the  blocks  and  leaves  the  pavement  cleaner  than 
it  would  without  it.     A  subsequent  occasional  light  sanding 
is  a  distinct  advantage  to  the  pavement. 

In  the  care  of  the  pavement  after  it  is  laid  American  cities 
fail  more  seriously,  perhaps,  than  in  any  other  particular.  Once 
laid,  the  pavement  is  often  expected  to  take  care  of 
itself  without  any  further  attention.  This  is  often  Repairs 
due  to  causes  beyond  the  control  of  the  engineer;  t^nance*1" 
but  the  fact  remains  that  such  treatment  may  go 
far  to  defeat  the  best  manufacture  and  construction.  In 
Europe  wood  pavements  are  cleaned  with  regularity  and  care. 
They  are  frequently  flushed  with  water  and  are  never  allowed 
to  dry  out,  as  they  often  do  to  an  excessive  degree  in  the 
summer  droughts  in  America.  They  are  sanded  at  regular 
periods,  as  well  as  on  any  occasions  of  special  slipperiness. 
Most  American  cities  appear  to  consider  that  such  maintenance 
as  is  given  in  Europe  is  impossible  here.  A  few,  however, 
do  give  adequate  care  to  their  pavements,  and  it  is  believed 
that  for  many  others  greater  attention  in  this  direction  would 
be  a  paying  investment  rather  than  an  expense. 


356  THE  ART  OF  ROADMAKING 

Practically  the  only  repairs  required  aside  from  replacing 
blocks  taken  up  to  get  at  water  and  gas  pipes,  etc.,  is  to 
remove  soft  or  decayed  blocks  and  to  insert  new  ones. 
The  hole  caused  by  a  single  decayed  block  is  speedily 
enlarged  by  the  impact  of  wheels  dropping  into  the  depres- 
sion. 


CHAPTER  XVII 
ASPHALT  PAVEMENTS 

ASPHALT  exists  in  various  forms  over  widely  distributed 
parts  of  the  earth,  and  has  been  in  somewhat  common  use  for 
different  purposes  since  the  dawn  of  history;    con- 
sequently   the    terms    employed    to    designate    it  eE 


have  been  varied.    The  following  definitions  are  gen- 

erally accepted  and  are  sufficiently  exact  for  ordinary  purposes: 

"  Bitumen   is   a   natural   hydrocarbon  .mixture   of   mineral 
occurrence,  widely  diffused  in  a  variety  of  forms  which  grade 
by  imperceptible  degrees  from  a  light  gas  to  a  solid,  some- 
times found  in  a  pure  state,  but  usually  intermixed 
with  organic  and  inorganic  matter.     The  bitumen 
series  includes  the  following,  in  order  of  their  density:  Natural 
gas,  natural  naphtha,  petroleum,  naphtha  (at  ordinary  tem- 
peratures soft  and  sticky),  asphalt  (at  ordinary  temperatures 
stiff  and  non-sticky),  glance  pitch  (dry  and  brittle). 

"  Asphalt  is  a  general  name  for  the  solid  forms  of  the  natural 
mineral    bitumen.     Asphalt    is    distinguished    from    coal    in 
being  soluble  in  bisulphide  of  carbon  and  in  ben- 
zole.    Coal,   peat,   etc.,    are   called   pyro-bitumens 
because    they    yield    an    artificial    bitumen    by    distillation. 
Asphalt  is  usually  found  associated  with  various  mineral  and 
organic   substances.     Asphalt  is  sometimes  popularly   called 
mineral   pitch   and   mineral   tar;     and   different   varieties   of 
asphalt  are  called  grahamite,  albertite,  gilsonite,  wurtzelite, 
imitatite,  turrellite,  etc. 

"The  term  '  asphalt'  is  the  English  equivalent  of  '  asphaltum/ 
the  Latin  form.  Asphalt  and  bitumen  are  frequently  used 
synonymously,  but  usually  in  paving  literature  bitumen  is 
employed  to  designate  the  valuable  hydrocarbon  compounds 
in  the  native  asphalt. 

357 


358  THE  ART  OF  ROADMAKING 

"Crude  asphalt  is  the  native  mixture  of  bitumen,  sand,  clay, 
water,  organic  matter,  etc. 

"  Refined  asphalt  is  the  native  mixture  after  it  has  been 
freed  wholly  or  in  part  from  water  and  organic  and  inorganic 
matter  by  being  heated.  Commercial  refined  asphalt  contains 
considerable  earthy  matter;  in  fact,  commercial  refining 
consists  virtually  in  driving  off  the  water  and  volatile  oils, 
and  incidentally  in  removing  a  little  earthy  matter. 
,  "Rock  asphalt  is  a  limestone  or  sandstone  naturally  im- 
pregnated with  asphalt.  Rock  asphalt  is  the  principal  form 
of  asphalt  used  in  Europe  for  paving  purposes  and  is  usually 
there  designated  as  '  asphalt.' 

/  "  Asphaltic  or  bituminous  limestone  is  a  limestone  naturally 
impregnated  with  asphalt. 

^'Asphaltic  or  bituminous  sandstone  is  a  sandstone  naturally 
impregnated  with  asphalt. 

"Compressed  asphalt.  In  Europe,  particularly  in  France, 
a  rock-asphalt  pavement  is  frequently  referred  to  as  being 
made  of  '  compressed  asphalt.' 

t  "Asphalt  mastic  is  a  term  frequently  applied  to  refined 
asphalt,  particularly  to  that  obtained  from  bituminous  rocks, 
and  is  usually  in  the  form  of  cakes,  which  are  melted  and  mixed 
with  sand  and  used  for  making  pavements  and  sidewalks. 

"Asphaltic  cement  is  refined  asphalt  which  has  been  mixed 
with  some  solvent  to  increase  its  plasticity,  adhesiveness 
and  tenacity. 

"Asphalt  pavement  is  a  pavement  composed  of  sand  or 
pulverized  stone  held  together  by  asphalt.  In  America  an 
asphalt  pavement  is  ordinarily  understood  to  be  a  compara- 
tively thin  layer  of  sand  held  together  by  asphalt  laid  upon 
a  bed  of  hydraulic  cement  concrete;  but  in  Europe  the  term 
asphalt  pavement  is  understood  to  be  a  comparatively  thick 
layer  of  asphaltic  limestone  or  asphaltic  sandstone  with  or 
without  a  hydraulic  concrete  base. 

"Asphaltic  concrete  is  broken  stone  bound  together  with 
asphaltic  cement."  * 

*  "Roads  and  Pavements,"  by  I.  O.  Baker,  p.  385. 


ASPHALT  PAVEMENTS  359 

In  going  back  to  the  earliest  times    in  which    asphalt  is 
known  to  have  been  used  it  is  necessary  to  refer  to  the  mineral 
pitch,  or  bitumen,  as  being  the  material  quoted.     The  first 
use  of  asphalt  spoken  of  was  the  cementing  in  the  erection  of 
the   Tower   of   Babel;     next   we   read   that    Noah 
pitched  the  Ark  within  and  without  ("  bituminabis 
cum  bitunrine"),  and  also  in  Genesis  we  read,  "  Et  asphaltus 
fuit  eis  vice  cimenti." 

Felltham  wrote  in  the  beginning  of  the  seventeenth  century 
of  the  "Bituminated  walls  of  Babylon";  the  source  of  its 
supply,  the  fountains  of  Is,  on  a  tributary  of  the  Euphrates, 
still  yelds  asphalt. 

Xenophon  speaks  of  the  Median  Wall  as  being  built  of  "  Burnt 
brick  laid  in  asphalt,"  and  Diodorus  Siculus  describes  the 
process  of  laying  the  walls  of  Nineveh  with  material  from  the 
same  source.  He  says:  "In  order  to  bind  the  bricks  they 
were  covered  with  a  layer  of  asphalt,  instead  of  simple  tempered 
clay,  and  were  arranged  in  courses,  and  between  each  thir- 
teenth course  a  bed  of  reed  canes  was  introduced."  The 
burning  of  Sodom  and  Gomorrah  has  been  attributed  to  the 
accidental  ignition  of  petroleum  or  bitumen,  but  the  word 
petroleum  not  having  been  known  to  ancient  writers,  the 
legend  probably  refers  to  maltha  or  bitumen.  Other  ancient 
authors  mentioning  asphalt  were  Herodotus,  Aristotle,  Strabo, 
Pliny,  and  Homer. 

The  Egyptians  spread  bitumen  upon  the  bandages  wound 
around  their  mummies,  and  its  wonderful  preservative  proper- 
ties in  this  connection  can  be  seen  in  the  museums  of  to-day. 
Asphalt  was  also  used  by  the  Egyptians  in  the  foundations  of 
the  Pyramids,  and  for  the  coating  of  the  external  and  internal 
walls  of  the  ground  floors  of  houses,  and  in  the  construction 
of  cisterns,  silos,  and  other  work  where  waterproofing  was 
necessary. 

It  will  be  seen,  therefore,  that  from  before  the  time  of  the 
Deluge,  asphalt  has  been  used  and  referred  to,  but  there  is  no 
record  of  its  use  for  street  paving  until  1838,  and  not  until 
1854  was  it  employed  to  any  great  extent.  The  laying  of 
macadam  roads  in  Val  de  Travers,  Canton  of  Neuchatel, 


360  THE  ART  OF  ROADMAKING 

Switzerland,  led  to  the  discovery  that  the  brown  bituminous 
limestone  rock,  found  in  the  district,  under  traffic  and  the 
summer  heat  became  welded  into  a  continuous  sheet. 

In  1854  some  streets  in  Paris  were  paved  with  this  ma- 
terial, and  it  was  introduced  into  London  in  1869.  The 
success  which  attended  these  early  pavements  led  to  its 
extensive  use  throughout  Europe,  and  to  its  introduction  into 
America. 

In  1870  the  first  sheet  asphalt  pavement  in  this  country  was 
laid  in  Newark,  N.  J.,  in  front  of  the  City  Hall.  In  1873 
a  small  piece  was  laid  in  Fifth  Avenue,  New  York,  and  a  few 
other  experimental  sections  were  laid;  but  its  first  test  on  a 
large  scale  was  in  1876  on  Pennsylvania  Avenue  in  Washington, 
D.  C.  Preceding  1882,  outside  of  Washington,  D.  C.,  there 
were  not  more  than  half  a  dozen  streets  in  this  country  paved 
with  any  form  of  asphalt;  but  since  that  date,  asphalt  pave- 
ments have  increased  so  rapidly  that  they  now  rank  first 
in  extent  of  use  and  in  satisfactory  qualities. 

These  pavements  were  at  first  made  of  materials  imported 
from  Europe,  but  the  great  cost  involved  made  the  pavement 
so  expensive  as  to  induce  American  inventors  to  seek  to 
manufacture  a  material  having  similar  qualities.  The  result 
was  the  introduction  of  many  substitutes  and  imitations,  the 
majority  of  which  proved  defective.  The  cost  of  the  imported 
material  and  the  failure  of  the  substitutes  directed  attention 
to  the  deposits  of  natural  bitumen  on  the  island  of  Trinidad, 
and  experiments  were  made  which  demonstrated  the  possi- 
bility of  making  a  mastic  with  this  bitumen  as  its  cementing 
material,  as  strong,  elastic,  and  durable  as  that  imported  from 
Europe;  but  it  was  only  after  some  years  that  this  process 
was  introduced  and  made  a  commercial  success. 

The  difference  between  the  asphalt  pavements  of  Europe 
and  those  of  America  is  due  to  the  character  of  the  materials. 
European  ^ne  ^ormer  are  composed  of  limestone  rock  natu- 
and  rally  impregnated  with  bitumen,  while  the  latter 

American  are  composed  of  an  artificial  mixture  of  bitumen, 
lts*  limestone,  and  sand.  The  limestone  in  the  Euro- 
pean pavements  becomes  hard,  smooth,  and  slippery  under 


ASPHALT  PAVEMENTS  361 

traffic,  and  is  thus  objectionable  for  general  use  in  frosty 
latitudes.  The  granular  nature  of  the  sand  used  in  preparing 
the  Trinidad  asphaltum  diminishes  the  tendency  to  wear 
smooth  and  materially  lessens  the  slipping  of  horses. 

Many  deposits  of  bituminous  rock  are  found  in  the  United 
States,  but  they  have  been  used  only  to  a  limited  extent, 
the  principal  sources  of  supply  at  present  being  the  Island  of 
Trinidad,  Bermudez,  Venezuela,  and  California. 

The  cost  of  preparing  the  different  varieties  of  asphaltum 
for  street  pavement  is  nearly  the  same;  and  as  all  appear  to 
be  about  equally  durable,  the  exclusive  use  of  any  one  of 
them  is  due  merely  to  local  conditions. 

An  artificial  asphalt  pavement  consists  primarily  of: 

1.  A  foundation  of  hydraulic   cement  concrete,  or  an  old 

pavement  of  cobblestones,  granite  blocks,  bricks,  etc. 

2.  A  binder  course  composed  of  broken  stone  and     .    .fi  . 

asphalt  cement.  sheet 

3.  A  wearing  coat  li  to  2  inches  thick  composed    asphalt 

of  asphaltic  paving  cement  mixed  with  sand.    Pavement- 
The  advantages  of  this  pavement  are: 

1.  Ease  of  traction. 

2.  Comparative  noiselessness  under  traffic. 

3.  Impervious  to  water. 

4.  Easily  cleaned. 

5.  Produces  neither  mud  nor  dust. 

6.  Pleasing  to  the  eye. 

7.  Suitable  to  all  classes  of  traffic. 

8.  No  vibration  or  concussion  in  travelling  over  it. 

9.  Expeditiously  laid,  causing  little  inconvenience  to  traffic. 

10.  Openings  to   gain  access  to   underground   pipes  easily 

made. 

11.  Durable. 

12.  Easily  repaired. 
The  defects  are: 

1.  Slippery  under  certain  conditions  of  the  atmosphere. 

2.  Disintegrates  if  excessively  sprinkled  or  otherwise  sub- 

jected to  constant  moisture,  although  asphaltum  is  im- 
pervious and  insoluble  in  either  fresh  or  salt  water. 


362 


THE  ART  OF  ROADMAKING 


FIG.  195. — Carroll  Street,  Brooklyn,  N.  Y.,  before  Covering  Cobble  Pavement  with 

Sheet-asphalt  in  1900. 

(From  Judson's  "City  Roads  and  Pavements."') 


ASPHALT  PAVEMENTS 


363 


F1G.  196.— Carroll  Street,  Brooklyn,  N.  Y.,  after  Paving  with  Trinidad  Sheet- 
asphalt  in  1900. 

(From  Judson's  "City  Roads  and  Pavements.") 


364  THE  ART  OF  ROADMAK1NG 

3.  Becomes  soft  under  traffic  in  extreme  heat  and  presents 

a  wavy  surface,  and  under  extreme  cold  may  crack  and 
become  friable. 

4.  Not  adapted  to  steep  grades. 

5.  Necessity    of    quick    repairs.     The    material    has    little 

coherence,  and  if  from  irregular  settlement  of  the  founda- 
tion or  local  violence,  a  break  occurs,  the  passing  wheels 
rapidly  shear  off  the  sides  of  the  hole.  This  is  prevented 
in  some  cities  by  the  constant  attention  of  workmen 
who  traverse  the  streets  with  a  light  repairing  outfit, 
and  wherever  a  defect  is  observed  it  is  patched  at 
once  and  so  effectually  that  the  spot  cannot  be  distm- 
guished. 

Asphaltum  itself  is  one  of  the  most  imperishable  substances 
in  nature.  Among  the  oldest  monuments  of  human  industry 
that  survive  are  constructions  of  asphalt.  With 
1  y'  asphalt  pavements  the  systems  adopted  for  main- 
tenance render  it  difficult  to  ascertain  the  actual  life  of  the 
pavement  under  traffic.  They  are  repaired  immediately  they 
need  it,  and  as  each  repair  is  so  much  new  material  laid,  the 
whole  surface  is  really  relaid  in  the  course  of  years.  Experience 
has  shown  that  asphalt  will  last  without  extensive  repairs 
from  four  to  six  years,  and  that  in  the  course  of  ten  years, 
the  entire  surface  will  have  been  renewed. 

Asphalt  is  to  a  certain  extent  elastic  and  does  not  begin 
to  wear  until  this  elasticity  is  overcome  by  thorough  com- 
pression. This  is  the  case  with  no  other  paving  material; 
stone  and  wood  begin  wearing  from  the  day  traffic  commences. 
Under  ordinary  traffic  it  may  be  estimated  that  it  will  take 
two  years  to  complete  the  compression  of  asphalt,  and  the 
weight  of  a  square  foot  of  this  pavement  will  at  the  expiration 
of  that  time  be  nearly  the  same  as  on  the  day  it  was  laid, 
though  the  thickness  is  reduced  during  the  first  two  years  as 
much  as  it  will  be  in  the  following  eight. 

The  extent  to  which  the  thickness  has  been  reduced  is  said 
to  be  as  much  as  one-fourth  the  original  thickness.  A  pave- 
ment in  Paris  which  had  lost  more  than  one-fourth  of  its 
thickness  was  found  to  have  lost  only  5  per  cent  of  its  weight 


ASPHALT  PAVEMENTS 


365 


after  sixteen  years'  use,  and  the  pavement  in  Cheapside,  London, 
after  fourteen  years'  use,  shows  a  reduction,  where  not  repaired, 
from  its  original  thickness  of  2\  to  If  inches. 


CONSTRUCTION  OF  THE  PAVEMENT 

The  sheet  asphalt  wearing  surface  has  no  power  in  itself 
to  support  the  traffic,  so  that  a  solid  unyielding  foundation 


FIG.  197. — Laying  Bituminous  Foundation,  Rome,  N.  Y. 

(From  Judson's  "City  Roads  and  Pavements.") 


Foundation. 


is  indispensable,  otherwise  the  weight  of  the  traffic  would  crush 

it.     If  the  street  has  never  been  paved,  the  base  of 

the  proposed  asphalt  pavement  is  made  of  hydraulic 

cement  concrete  4  inches  thick  for  light  traffic,  or  6  inches 

for  heavy  city  traffic. 

Sometimes  the  asphalt  is  laid  upon  a  bituminous  concrete, 
the  advantage  claimed  being  that  the  asphalt  adheres  more 
firmly  to  it  than  to  the  hydraulic  concrete  and  prevents 
weather  cracks  and  waves.  It  is  also  less  expensive,  but  repairs 


366  THE  ART  OF  ROADMAKING 

are  more  difficult.     This  form  of  foundation  has  never  been 
common  and  is  now  very  little  used. 

With  cement  concrete,  the  bond  between  the  foundation 
and  the  wearing  surface  is  not  very  great,  hence  it  is  very 
easy  to  strip  off  the  surface  in  case  repairs  are  necessary; 
but  it  sometimes  slips  on  the  foundation,  and  rolls  into  waves 
and  irregular  surfaces,  and  sometimes  cracks  with  sudden  and 
great  changes  of  temperature.  A  cement  concrete  foundation 
must  be  set  and  thoroughly  dry  before  the  asphalt  is  laid, 
as  the  best  asphalt  laid  in  the  most  skilful  manner  on  first-class 
but  damp  concrete  will  rapidly  go  to  pieces.  When  the  hot 
asphalt  is  applied  to  a  damp  surface  the  water  is  immediately 
sucked  up  and  turned  into  steam,  which  tries  to  escape  through 
the  heated  material;  the  result  is  that  coherence  is  prevented, 
and,  although  the  surface  of  the  asphalt  is  smooth,  the  mass  is 
really  disintegrated  from  underneath  by  the  water.  As  soon 
as  the  pavement  is  subjected  to  the  action  of  traffic,  the  fissures 
formed  by  the  steam  appear  on  the  surface,  and  the  whole 
pavement  quickly  falls  to  pieces.  For  the  same  reason  asphalt 
should  be  laid  only  in  dry  weather. 

The  binder  course  consists  of  a  layer  about  1J  inches  thick 

of   broken   stone   cemented   together   with   asphaltic    paving 

cement  and  rolled  in  place  while  hot.     This  binds 

the  wearing  coat  and  the  foundation  together,  and 

prevents  the  former  from  lifting  from  the  latter 

or  being  pushed  along  in  a  wave.     On  account  of  the  expense 

of  maintaining  the  necessary  appliances  for  mixing  the  stone 

and  asphalt  of  the  binder  course,  this  course  is  sometimes 

omitted,  and  a  thin  course  of  material  of  the  same  composition 

as  the  wearing  coat  is  laid  instead,  and  is  called  a   "cushion 

coat."     This  is  usually  from  J  to   1  inch  thick,   and   being 

richer  in  cement  adheres  more  firmly  to  the  foundation  than 

would  the  top  coat. 

Composition      Asphaltum  in  a  refined  or  pure  state  is  valueless  as 
of  wearing  . .  , .  ••'»<• 

surface.        a  cementing  medium,  owing  to  its  hardness,  brittle- 
ness,  and  lack  of  cementitious  properties;  therefore 
it  is  necessary  to  add  some  substance  which  will  impart  to 
it   the   required    plastic,    adhesive,    and    tenacious   qualities. 


ASPHALT  PAVEMENTS  367 

This  substance  must  be  one  that  will  partially  dissolve  the 
asphaltene  and  form  a  chemical  union  by  solution  instead  of 
a  mechanical  mixture.  The  duty  which  it  has  to  perform  is 
an  important  and  peculiar  one:  if  it  is  a  perfect  solvent  of  the 
constituents  of  the  bitumen,  the  adhesive  qualities  will  be 
destroyed;  if  it  is  an  imperfect  one,  the  asphaltum  will 
retain  its  brittleness. 

This  prepared  cement  is  termed  the  "matrix,"  and  forms 
one  of  the  two  essential  parts  of  asphalt  cement  pavements, 
the  other  part  being  the  "aggregate."  The  success  or  failure 
of  the  pavement  will  depend  upon  the  care  exercised  in  the 
selection  of  these  materials  and  the  skill  displayed  in  com- 
bining them  and  laying  the  pavement.  Each  has  a  distinct 
function  to  perform:  the  cementing  material,  or  the  matrix, 
preserves  the  coherency  of  the  mass;  the  resisting  material, 
or  the  aggregate,  resists  the  wear  of  the  traffic. 

The  aggregate  consists  of  sand  and  stone  dust  or  Portland 
cement.  The  sand  must  be  clean  and  free  from  loam  and 
vegetable  impurities,  and  it  should  be  composed  of  angular 
grains  ranging  from  coarse  to  fine  and  having  as  small  a  pro- 
portion of  voids  as  possible. 

In  the  making  of  the  wearing  surface,  the  asphaltic  cement 
and  the  sand  are  separately  heated.     The  proper  amount  of 
cement  and  sand  are  weighed  out  and  simultaneously    Mixin  and 
poured  into  a  mechanical  mixer  consisting  of  two    spreading 
sets  of  interlocking  revolving  blades  which  thor-    wearing 
oughly    mix    the    materials,    the    process    usually 
requiring  1  to  1£  minutes.     When  completed,  sliding  doors  in 
the  bottom  of  the  mixer  are  opened,  and  the  material  drops 
out  into  carts  or  wagons  which  carry  it  to  the  street. 

The  mixed  cement  and  sand  is  brought  upon  the  street 
at  a  temperature  of  about  280°  F.  It  is  dumped  upon  the 
binder  course  and  evenly  spread  over  the  surface  with  shovels 
and  rakes,  precautions  being  taken  that  no  leaves,  straw, 
pieces  of  paper,  or  other  rubbish  become  mixed  with  the 
paving  mixture.  Care  must  be  taken  to  secure  an  even  dis- 
tribution of  the  loose  material  to  prevent  the  formation  of 
depressions  or  elevations  in  the  finished  surface.  The  depth 


368 


THE  ART  OF  ROADMAKING 


ASPHALT 2" 


a.  Asphalt  on  Stone  Blocks. 


b.  Asphalt  on  Macadam. 


ASPHALT  2 
BINDER     jfe 


CONCRETES* 


c.  Heavy  Traffic  Pavement. 


WM  ASPHALTS" 

CONCRCTZ+' 


d.  Light  Traffic  Pavement. 

FIG.  198.— Type  Sections  of  Asphalt  Pavements. 


ASPHALT  PAVEMENTS 


369 


of  the  mixture  is  regulated  by  chalk  lines  on  the  curb,  by  the 
length  of  the  teeth  of  the  rake,  and  sometimes  by  rods  sup- 
ported on  feet  of  a  length  sufficient  to  bring  the  top  of  the 
rod  to  the  level  of  the  uncompacted  asphalt  mixture.  The 
thickness  after  being  rolled  is  usually  about  2  inches. 

The  first  compression  is  given  by  hand  rollers  and  tamping 


Coucrttc  Tamper 


FIG.  199. — Tools  and  Appliances  for  Laying  Asphalt  Surface. 

irons.  The  hand  roller  has  a  fire-pot  inside  for  heating  it,  and 
the  tamping  irons,  which  are  used  around  manhole  covers  and 
curbs,  etc.,  where  the  roller  cannot  conveniently  be  used,  are 
heated  in  a  fire  in  an  iron  basket,  which  is  moved  from  place 
to  place  on  wheels. 

After  this  first  compression,  men  with  tamping  and  smooth- 
ing irons,  finish  the  gutters,  joints,  and  all  angles  which  cannot 
be  reached  with  the  heavier  rollers. 


370 


THE  ART  OF  ROADMAKING 


The  first  compression  having  been  given,  some  natural 
hydraulic  cement  or  any  impalpable  mineral  matter  is  dusted 
over  the  surface  to  give  it  a  more  pleasing  color  and  to  prevent 
adhesion  to  the  roller;  and  then  the  surface  is  rolled  with  a 
special  pattern  of  steam-roller,  until  the  roller  leaves  no  mark. 
This  rolling  should  closely  follow  the  spreading  of  the  material, 
so  that  it  shall  not  have  time  to  cool  before  the  final  com- 
pression is  obtained.  The  state  of  the  weather  is  also  an 
element  to  be  considered,  for  if  a  strong  wind  be  blowing,  the 


FIG.  200. — Hand  Asphalt  Roller  with  Fire-pot. 

material,  spread  over  a  broad  surface  only  2  to  3  inches  thick, 
will  cool  much  more  rapidly  than  on  a  calm  day,  even  if  the 
temperature  is  considerably  lower. 

When  the  rolling  is  completed,  the  pavement  may  be  thrown 
open,  as  traffic,  if  not  too  heavy,  is  of  advantage  to  a  newly- 
laid*  asphalt  pavement,  since  the  pressure  of  the  wheels  aid 
in  consolidating  the  wearing  coat  and  in  closing  the  surface. 

The  top  of  the  binding  course  should  be  perfectly  dry  when 
the  wearing  surface  is  laid,  to  prevent  its  being  separated 
from  the  course  below  by  the  formation  of  steam.  Asphalt 


ASPHALT  PAVEMENTS 


371 


FIG.  201. — Street  Kettle  for  Asphalt, 


FIG.  202. — Asphalt  Gutter  Painters. 


372 


THE  ART  OF  ROADMAKING 


should  not  be  laid  in  cold  weather,  as  the  paving  mixture  may 
become  chilled  between  the  mixing  plant  and  the  street,  and 
particularly  when  it  comes  in  contact  with  the  cold  foundation. 
The  chief  points  requiring  skill  in  the  spreading  of  the 
asphalt  surface  are: 

1.  To  avoid  inequalities  of  the  surface,  especially  depressions 
which  prevent  the  rapid  removal  of  storm  water. 


a.  Gutter  in  which  Water  Flows. 
FIG.  203. — Action  of  Water  on  Gutters  of  Street  Paved  with  Asphalt. 

2.  To  secure  thorough  consolidation  of  the  gutters,  which 

otherwise  rot  rapidly. 

3.  To  give  it  a  thorough  rolling;  the  asphalt  mixture  cannot 

be  fully  compacted  by  simple  pressure,  but  requires  the 
kneading  action  of  repeated  passages  of  the  roller. 

r  ailures  of 

asphalt  There   have    been    frequent    failures    of    asphalt 

pavements.    pavements,  which  may  have  been  due  to  any  one, 
or  more,  of  the  following  causes: 


ASPHALT  PAVEMENTS 


373 


Unsuitable  Materials: 

Asphaltum  which  has  been  so  changed  by  natural  causes 
as  to  possess  little  or  no  cementing  power. 

Fluxing  agents,  such  as  those  which  are  not  solvents  of 
asphaltene,  and  thus  form  a  mechanical  instead  of  a 
chemical  union,  or  such  as  those  which,  for  other 
causes,  render  the  pavement  brittle,  in  which  condition 
it  is  easily  broken  up  under  the  action  of  the  traffic. 


6.  Gutter  Carrying  no  Water. 
FIG.  203.— Action  of  Water  on  Gutters  of  Street  Paved  with  Asphalt. 


Sand,  either  too  coarse  or  too  fine,  or  containing  loam, 
vegetable  matter,  or  clay. 

Free  oil  in  binder. 
Improper  Manipulation: 

Too  high  heat  in  refining  the  crude  asphaltum,  which 
reduces  or  entirely  destroys  its  cementing  qualities. 

Improper  consistence:  if  the  cement  is  too  hard,  the  pave- 
ment will  have  a  tendency  to  crack  during  cold  weather; 


374  THE  ART  OF  ROAD  MAKING 

and  if  too  soft,  if  will  push  out  of  place  and  form  waves 
under  the  traffic. 

Insufficient  quantity  of  cement.  This  varies  with  the 
character  of  the  sand — a  fine  sand  requires  more 
cement  than  a  coarse  one,  and  the  proportion  of  cement 
must  be  varied  to  suit  the  character  of  the  sand  to 
be  used. 

Inadequate  mixing  of  ingredients,  whereby  the  cement 
and  the  particles  of  sand  are  not  brought  into  intimate 
contact. 

Rich  binder.  If  an  excess  of  asphalt  or  coal-tar  is  used 
in  the  binder  course,  it  is  likely  to  work  to  the  surface 
and  then  becoming  absorbed  by  the  wearing  surface, 
cause  it  to  disintegrate. 

Chilling  of  the  cement  while  being  transported  from  the 
mixing  plant  to  the  street. 

Separation  of  the  cement  and  sand.  If  the  distance  from 
the  plant  to  the  street  is  long  and  there  is  any  unusual 
delay,  some  of  the  asphaltic  cement  may  work  to  the 
bottom  of  the  load,  and  when  the  material  is  dumped 
there  will  be  both  rich  and  lean  spots,  both  of  which 
are  equally  objectionable. 

Laying  the  paving  composition  on  a  damp  or  dirty 
foundation,  prevention  it  from  uniting  firmly  with  the 
foundation. 

Inadequate  compression,  thus  allowing  the  admission  of 
rain  and  other  water  falling  upon  the  surface  of  the 
pavement,  with  its  destroying  effects. 
3.  Natural  Causes: 

All  materials  in  nature  are  undergoing  changes  due  to  the 
action  of  the  elements,  and  asphaltum  is  no  exception. 

Ordinary  wear  decreases  the  thickness,  due  to  the  loss  of 
material  by  the  abrasion  of  hoofs  and  wheels,  but  in  the 
case  of  asphalt  pavements  this  loss  of  material  is  very 
slight. 

Natural  decay.  Under  the  action  of  heat  and  water  all 
bitumens  undergo  a  change,  and  when  the  maximum 
of  hardness  is  attained,  natural  decay  sets  in,  and 
under  the  combined  action  of  the  elements,  the  mate- 
rial gradually  rots  and  disintegrates. 

Weak  or  insufficient  foundation  will,  by  unequal  settle- 
ment, cause  cracks  and  depressions  in  the  asphalt  sur- 
face which,  under  traffic,  will  speedily  enlarge. 

Leaky  joints  with  curbs,  crossings,  etc.,  which  permit  the 
entrance  of  water  under  the  asphaltic  covering. 


ASPHALT  PAVEMENTS 


375 


Porous  foundation,  which  permits  the  ground-water  to 
rise,  by  capillary  action,  to  the  underside  of  the  wearing 
surface,  where  by  freezing  it  may  break  the  bond 
between  the  top  layer  and  the  base,  and  thus  permit 
the  wearing  surface  to  be  pushed  out  of  place  and 
broken. 

Illuminating  gas,  escaping  from  leaky  pipes  under  the 


FIG.  204. — Destructive  effects  of  Gas  Leaks  on  Asphalt  Pavement. 

(From  Judson's  "  City  Roads  and  Pavements.") 

pavement,  is  absorbed  by  the  pavement,  and  causes  the 

disintegration  of  the  asphalt. 
Cracks,  due  to  the  contraction  of  the  wearing  surface,  after 

the  pavement  has  lost  part  of  its  cementing  power  by 

several  years  use. 
Shifting  under  traffic,  due  to  too  soft  a  wearing  surface. 

Bonfires  which  are  sometimes  built  upon  the  asphalt 

pavement  are  likely  to   cause  considerable 

damage.  RePairs- 

The  repairs  necessary  in  the  maintenance  of  asphalt  pave- 
ments may  be  classified  as  those  due  to: 


376  THE  ART  OF  ROADMAKING 

1.  Settlement  of  the  subgrade. 

2.  Disintegration  of  the  pavement  in  spots. 

3.  Formation  of  waves. 

4.  Formation  of  cracks. 

5.  Disintegrating  effect   of  water   in  the   asphalt   gutters, 

necessitating  frequent  "painting"  with  rich  asphalt  or 
bitumen. 

6.  Defects  next  to  the  street-car  rails,  crossing  stones,  man- 

hole covers,  etc. 


FIG.  205.— Surface  Heater  for  Repairing  Asphalt  Pavements. 


ASPHALT  BLOCK  PAVEMENT 

The  manufacture  of  paving  blocks  from  crushed  stone  and 
asphaltic  cement  was  begun  in  San  Francisco  in  1869,  but  in 
consequence  of  imperfectly  prepared  materials  and 
crude  appliances,  the  blocks  were  weak  and  friable 
and    the    results    were    unsatisfactory.      Improve- 
ments   have  been  made  since  that  time  in  both  the  proc- 
esses   and    the    machinery,    resulting    in    the    production    of 
tougher  and  more   durable   blocks,   which  are  now  used  ex- 
tensively in  various  parts  of  the  United  States. 

The  blocks  are  composed  of  crushed  stone  and  asphaltic 
cement  in  the  proportions  of  87  to  90  per  cent  of  stone  and 
13  to  10  per  cent  of  cement.  The  materials  are  heated  to 
300°  F.  and  are  mixed  in  a  rotary  mixer  until  all  the  faces  of 
every  particle  of  the  crushed  stone  are  perfectly  coated  with 
the  mixture  of  asphaltic  cement  and  limestone  dust.  The 


ASPHALT  PAVEMENTS  377 

product  is  then  put  in  molds  12  inches  long,  4  or  5  inches  wide, 
and  3  or  4  inches  deep,  and  subjected  to  a  pressure  of  2  to  2£ 
tons  per  square  inch  and  then  slowly  cooled  in  water.  The 
blocks  weigh  from  22^  to  24  pounds  each,  according  to  the 
specific  gravity  of  the  stone  employed,  and  about  twenty-six 
blocks  are  required  per  square  yard. 

The  blocks  are  laid  on  the  street  in  close  contact,  in  the 
same  manner  as  stone  paving  blocks,  either  with  or  without 
an  artificial  foundation,  the  foundation  usually  employed  being 
gravel,  or  gravel  and  sand,  or  sand  alone. 

The  advantages  and  defects  of  the  sheet  asphalt  pavement 
are  equally  applicable  to  asphalt  block  pavements,  but  they 
have  the  special  advantage  over  "sheet  asphalt"  in  that  they 
can  be  made  at  a  factory  located  near  the  materials,  whence 
they  can  be  transported  to  the  place  where  they  are  to  be 
used,  and  laid  by  ordinary  pavers  without  the  aid  of  skilled 
labor;  whereas  sheet  pavements  require  special  machinery 
and  skilled  labor  in  each  city  where  they  are  laid. 

Compared  with  stone  blocks  they  are  much  smoother  and 
less  noisy,  and  they  form  a  practically  impervious  pavement, 
because  under  the  action  of  the  sun  and  traffic  the  asphalt 
cements  the  blocks  together. 

For  narrow  well-travelled  streets  they  do  not  make  a  suitable 
pavement,  but  where  the  traffic  is  of  such  a  character,  as  on 
residence  streets,  to  warrant  their  use  they  make,  when  laid 
upon  a  concrete  foundation,  an  excellent  pavement,  smooth, 
durable,  and  easily  cleaned,  healthy,  and  pleasant  to  the  eye. 

COAL-TAR  PAVEMENTS 

In  their  earlier  construction,  the  wearing  surface  of  coal-tar 
pavements  consisted  essentially  of  small  gravel,  sand,  and 
stone  dust,  cemented  by  a  product  of  coal-tar.  In  the  later 
pavements,  a  certain  proportion  of  bitumen  is  mixed  with  the 
tar  with  beneficial  results. 

Wherever  laid  in  the  United  States,  coal-tar  pavements,  as 
a  rule,  have  given  little  satisfaction,  their  failure  being  due  to 
the  presence  of  volatile  oils  in  the  tar,  which  on  exposure  to 


378  THE  ART  OF  ROADMAKING 

atmospheric  influence  slowly  oxidize  and  become  inert,  thus 
destroying  the  cementing  qualities  of  the  tar.  If  these  oils 
are  removed  before  the  tar  is  used  the  resulting  material  is 
brittle,  and  soon  crumples  to  pieces  after  being  laid.  Coal-tar 
is  also  very  sensitive  to  heat:  in  summer  it  is  soft,  in  winter 
brittle.  On  account  of  these  defects,  the  use  of  coal-tar  alone, 
as  a  cementing  material  for  pavements,  has  been  almost 
entirely  abandoned. 

To  overcome  the  defects  of  coal-tar  when  used  alone,  the 
practice  has    arisen  of   mixing  the  gas   tars  with 

Coal-tar  bitumen,  and  this  has  been  successful  in  propor- 
and  asphalt.  . 

tion  to  the  amount  of  the  bitumen  used. 

Advantages  of  coal-tar  and  asphalt  pavement  are: 

1.  Cheapness. 

2.  A  surface  more  granular  and  less  slippery  than  asphalt. 

3.  The  binder  binds  the  base  and  wearing  surface  firmly 
together  and  eliminates  to  a  great  extent  the  faults  of  weather 
cracks  and  wave  surfaces. 

4.  Can  be  laid  from  curb  to  curb,  as  it  will  not  "rot"  in  the 
gutters  as  does  the  asphalt. 

5.  Low  cost;    pavements  constructed  of  carefully  selected 
and  combined  materials  and  properly  laid  will  cost  but  little, 
if  any,  more  than  the  asphalt  for  maintenance. 

Defects  of  coal-tar  and  asphalt  pavement  are: 

1.  The  wearing  surface  consists  of  75  per  cent  of  coal-tar, 
which  material  can  rarely  be  obtained  of  uniform  quality. 

2.  The  wearing  surface,  being  only  1J  inches  thick,  requires 
renewal  at  frequent  intervals. 

3.  The  pavement  is  not  so  pleasing  to  the  eye  as  asphalt 
in  color. 

4.  The   use   of   the   bituminous   base   gives   rise   to   many 
problems  in  the  grade  of  the  streets  on  which  it  is  used,  due 
to  the  fact  that  the  base,  the  binder,  and  the  wearing  surface 
coalesce  so  as  to  form  a  solid  mass.     The  wear  on  the  surface 
is  never  quite  uniform;   and  when  the  binder  or  base  becomes 
exposed  on  the  most  travelled  part  of  the  street,  the  pavement 
near   the   gutter   may   be   worn   but    slightly.     To   resurface 
properly,  the  remnants  of  the  old  surface  must  be  removed, 


ASPHALT  PAVEMENTS  379 

and  the  new  surface  laid  directly  upon  the  binder.  It  is, 
however,  impracticable  to  strip  a  coal-tar  surface.  It  may 
be  broken  by  the  pick  and  bar,  but  it  breaks  as  readily  in  the 
base  or  binder  as  at  the  original  line  of  demarcation.  In 
fact,  there  is  no  such  line.  The  practice  is  to  cut  out  what 
may  be  necessary  near  the  curb  and  put  a  new  surface  on  the 
roadway  as  it  stands.  The  result  is  to  raise  the  level  of  the 
roadway  at  every  resurfacing,  or,  if  the  original  level  at  the 
curb  be  maintained  by  the  method  of  cutting  out  as  stated, 
to  increase  the  crown  of  the  street;  but  as  such  pavements 
will  not,  as  a  rule,  require  resurfacing  at  more  frequent  intervals 
than  every  fifteen  years,  and  as  the  surfacing  should  not 
raise  the  level  more  than  one-half  inch,  the  upward  growth 
will  not  exceed  3^-  inches  per  century. 

If  the  surface  is  tarred  over  every  year  with  a  brush  and 
sprinkled  with  sand,  the  life  is  lengthened. 


CHAPTER  XVIII 
CONCRETE   PAVEMENTS 

PORTLAND  CEMENT  forms  in  combination  an  artificial  stone 
which  increases  in  hardness  and  strength  with  age;  it  is 
displacing  natural  stone  in  many  kinds  of  construction  and 
has  recently  had  much  consideration  as  a  paving  material. 
Concrete  has  long  been  used  for  the  foundation  of  pavements 
(see  page  399)  and  in  a  few  cities,  principally  in  Philadelphia, 
alleys  have  been  paved  with  concrete  laid  in  the  same  manner  as 
for  sidewalks,  but  owing  to  its  high  cost,  concrete  has  not  met 
with  the  approval  of  leading  paving  authorities  for  the  wearing 
surface  of  roadways.  This  principal  objection  may  be  said 
to  have  been  met  now  that  the  enormous  growth  in  its  pro- 
duction has  greatly  decreased  its  cost,  and  its  use  for  highway 
purposes  will  undoubtedly  increase. 

In  recognition  of  the  growing  importance  of  concrete  in 
road  construction,  the  Committee  on  Concrete  Review  of 
the  Association  of  American  Portland  Cement  Manufacturers 
offered  two  prizes,  one  of  $75  and  one  of  $25,  for  articles  on 
this  subject,  the  medium  selected  for  publication  being  Good 
Roads  Magazine* 

*  The  first  prize  was  awarded  to  Ernest  McCullough,  C.E.,  Chicago, 
and  the  second  prize  to  Charles  W.  Ross,  C.E.,  Street  Commissioner  of 
Newton,  Mass.,  On  the  subject  of  the  awards  the  Committee,  whose 
members  were  George  W.  Tillson,  E.  L.  Powers,  and  Percy  H.Wilson, 
sent  the  following  communication  to  Albert  Moyer,  of  New  York,  Chair- 
man of  the  Committee  on  Concrete  Review: 

"The  Jury  of  Award  appointed  to  judge  the  papers  submitted  through 
the  Good  Roads  Magazine,  met  on  March  19,  1909,  and  after  carefully 
considering  the  merits  of  the  papers  presented,  decided  to  award  the 
first  prize  of  $75  to  paper  No.  2099. 

"Our  reasons  for  doing  this  were:  First,  on  account  of  the  able  dis- 
cussion of  the  merits  of  a  concrete  roadway  as  compared  with  roadways 
built  of  other  materials;  and,  second,  owing  to  the  comprehensive  details 

380 


CONCRETE  PAVEMENTS  381 

The  advantages  of  concrete  as  a  paving  material,  and  the 
methods  of  its  application  as  brought  out  in  the  first  prize 
paper  and  summarized  in  this  chapter,  constitute 
all  the  available  information  on  the  subject,  based   Advantages 
on   the   experience   of   a   practical   road   engineer.    Concrete 
Mr.  McCullough  has  endeavored  to  show  that  con- 
crete offers  a  paving  material  containing  an  extremely  large 
per  cent  of  all  the  desirable  qualities  given  in  Baker's  table 
of  relative  values    (page  29)   of  the   items  forming  an  ideal 
pavement,  and  in  almost  the  exact  ratios. 

In  respect  to  first  cost  concrete  is  without  a  competitor, 
for  the  materials  lie  within  easy  reach  of  all  who  want  paving 
material.  Few  districts  are  without  stone  good 
enough  for  the  main  body  of  the  pavement  and 
when  sand  is  not  to  be  had  readily,  crushed  stone  is  good. 
The  binding  element,  the  cement,  is  within  the  reach  of  every 
village,  town  and  city  in  the  country  at  approximately  two 
dollars  per  barrel,  and  a  very  small  amount  of  this  is  required 
when  proper  methods  are  adopted  to  proportion  the  concrete. 
There  are  no  patents  to  conflict,  so  that  every  man  who  can 
mix  concrete  may  become  his  own  paving  contractor.  The 
principal  question  in  the  selection  of  paving  materials  is  this 
one  of  first  cost,  and  the  desire  so  many  have  to  see  all  their 
money  spent  near  home,  which  has  always  been  a  source  of 
trouble,  will  not  be  so  hard  when  concrete  is  more  generally 
adopted.  It  is  the  one  material  that  is  low  in  first  cost  and 
yet  economical  in  the  end. 

The  presence  to-day  of  the  magnificent  roadways  of  old 
Rome  gives  evidence  of  the  low  cost  from  the  maintenance 
standpoint  of  a  properly  constructed  concrete 

pavement.     All  that  is  necessary  is  to  do  the  work    °? 
.  .  .  maintenance. 

right.     The    setting    of    concrete    is    a    process  of 
crystallization,  that  proceeds  best  when  just  enough  moisture 

of  construction;    third,  that,  in  our  opinion,  when  constructed  it  would 
make  the  best  roadway  of  those  discussed  in  the  papers. 

"The  second  prize  of  $25  we  awarded  to  paper  No.  2101.  First,  because 
of  the  comprehensive  description  of  a  concrete  roadway  which  can  be 
used  for  country  work,  and,  second,  because  of  the  logical  manner  in 
which  the  whole  subject  has  been  treated." 


382 


THE  ART  OF  ROADMAKING 


CONCRETE  PAVEMENTS  383 

can  reach  the  concrete.  This  process  continues  for  years.. 
Concrete  roadbeds  being  embedded  in  the  earth,  where  they 
will  be  continually  kept  moist  by  the  water  absorbed  from  the 
soil,  and  wet  almost  daily  by  rain  or  snow  from  above,  must 
grow  stronger  with  age  and  it  then  becomes  merely  a  question 
of  doing  the  work  properly  at  first.  This  means  careful 
selection  of  the  cement,  the  sand  and  the  principal  aggregate , 
the  mixing  and  the  depositing,  and  the  prevention  of  jarring 
until  the  material  shows  evidence  of  having  set  enough  to 
withstand  ordinary  traffic. 

The  manufacture  of  Portland  cement  has  reached  so  perfect 
a  plane  that  little  or  no  trouble  can  be  experienced  in  the 
cement.  More  trouble  arises  from  improper  selection  of  sand 
and  stone  and  poor  mixing  than  from  the  cement  used,  for 
to-day  American  Portland  cement  is  a  standard  article  pro- 
duced by  thousands  of  mills  all  working  to  turn  out  a  product 
that  will  pass  tests  that  are  standard  over  the  whole  world. 
Therefore  it  can  be  truthfully  said  that  a  properly  constructed 
concrete  roadway  is  the  lowest  in  cost  of  all  roadways  from 
the  standpoint  of  maintenance  and  is  practically  everlasting. 
The  elements  do  not  affect  it.  It  is  impervious  to  acids, 
gases,  oils  and  all  the  other  things  that  attack  other  paving 
materials  and  it  requires  no  coating  with  costly  materials 
to  protect  it. 

Tractive  resistance  can  be  shown  best  bv  com-          ase .° 

traction, 
panson  with  other   materials.     An  estimate  made 

in  Indiana  years  ago  gave  the  following  costs  for  horse-power 
per  ton  mile  to  haul  goods  over  various  pavements: 

Asphalt 2.7  cts. 

Block  stone  pavement  (average) 5.3  ' ' 

Macadam  in  good  order 8.0  " 

Gravel  road 8.8  " 

Earth  road,  hard  and  dry 18.0  " 

Macadam  with  ruts 26.0  ' ' 

Wet  sand 32.0  " 

Earth  road  with  ruts  and  mud 39.0  " 

Dry  sand 64.0  " 


384 


THE  ART  OF  ROADMAKING 


IJ 

Si: 


CQ 


CONCRETE  PAVEMENTS  385 

No  mention  is  made  of  wood  or  of  brick  but  experiments 
made  in  many  places  indicate  that  these  materials  are  prac- 
tically on  a  par  with  asphalt.  On  this  point  the  following 
table  gives  the  force  required  to  draw  one  ton  on  * 

Material. 

Iron 10  Ibs. 

Asphalt 15  " 

Wood 21  " 

Best  stone  blocks 33  ' ' 

Inferior  stone  blocks 50  " 

Average  cobble  stone 90  " 

Macadam 100  " 

Earth 200  " 

Considering  that  a  concrete  roadway  may  be  made  per- 
fectly smooth  if  desired,  or  can  be  roughened  as  much  as 
the  contractor  thinks  is  right,  it  is  hard  to  fix  a  value  that 
will  represent  ease  of  traction.  It  may  be  made  fully  as 
smooth  as  iron  if  desired,  and  thus  present  exactly  the  same 
resistance  value,  or  it  may  be  cut  into  block  form  to  resemble 
a  first-class  Belgian  block  pavement  and  thus  have  a  value 
equal  to  that  set  for  the  best  stone  blocks.  Expressing  it 
in  cost  per  ton-mile  it  may  range  from  one  cent  to  six  cents. 
There  is  never  any  occasion  for  it  to  be  higher  as  the  material 
is  more  easily  repaired  than  any  other  and  a  good  surface 
may  always  be  maintained. 

Good    foothold    depends    entirely    upon    surface,    and    the 
top  surface  is  capable  of  so  many  degrees  of  roughness  that 
the   pavement,   properly   constructed   and   finished 
will  never  offer  a  poor  foothold  for  horses  and  will 
always    have    a    good    surface    for    automobiles.     Should    it 
become  too  hard  and  smooth,  it  is  a  very  easy  and  inexpensive 
matter  to   roughen  the   surface.     Any  desired   finish   can  be 
given  it  and  thus  all  objections  on  the  ground  of  lack  of  good 
foothold  can  be  removed. 

*  Captain  (now  General)  Francis  V.  Greene,  in  Harper's  Wetkly,  of 
August  10,  1889. 


386 


THE  ART  OF  ROADMAKING 


CONCRETE  PAVEMENTS  387 

Concrete  is  not  so  noisy  as  other  pavements,  in  spite  of 
its  being  a  hard  pavement, — a  fact  borne  out  by  residents 
on  streets  paved  with  concrete.  The  reason  is 
easy  to  find.  Like  asphalt,  it  is  smooth  so  that 
wagons  going  over  the  surface  make  a  minimum 
of  noise.  It  has,  however,  the  advantage  that  the  pavement 
and  foundation  are  monolithic.  When  bricks  or  paving 
block  j  are  used  there  must  be  a  concrete  base.  It  often 
happens  that  an  arching  action,  caused  by  the  effect  of  the 
temperature  in  the  pavement,  makes  it  rise  above  the  founda- 
tion base  in  places  and  producing  a  rumbling  noise  that  is 
very  distressing  at  times.  Therefore,  expansion  joints  are 
placed  at  frequent  intervals  in  the  pavements  laid  on  a  con- 
crete base.  The  concrete  pavement  consisting  only  of  the 
concrete  base  used  for  other  pavements  arid  a  finish,  there 
can  be  no  separation  to  cause  a  rumbling,  and  outside  of 
this,  noise  is  caused  only  by  the  condition  of  the  surface  which 
is  entirely  within  the  control  of  the  men  putting  down  the 
roadway. 

Ease   of   cleaning   and  healthfulness   should   be   considered 
together.     A  concrete  pavement  can  be  washed  with  a  hose 
at  any  time,  and  as  it  contains  no  joints,  no  dirt 
can     collect    on    the    surface.     Its    healthfulness,  Cleanliness 
therefore,    cannot    be    questioned.     It    yields    no  fulness 
detritus  of  itself  and  therefore  the  mud  and  dust 
that  may  appear  on  the  surface  must  be  brought  on  by  wagon 
wheels  from  other  streets,  or  is  thrown  on  in  other  ways.     In 
itself  a  concrete  pavement  is  absolutely  free  from  mud  and 
dust. 

Concrete  is  one  of  the  poorest  conductors  of  heat  known 
and  being  light  colored  is  a  reflector  of  heat  rather  than  an 
absorber.  It  has  been  noticed  that  cement  side- 
walks after  nightfall  are  much  cooler  to  the  touch 
than  asphalt  paved  roadways  and  early  in  the 
mornings  the  cement  sidewalks  are  cool  to  the  hand,  while 
the  roadway  paved  with  asphalt  is  still  warm  from  the  heat 
absorbed  the  day  before.  A  pavement  that  is  highest  in  ease 
of  traction;  offers  perfect  foothold  for  animals  and  a  perfect 


388  THE  ART  OF  ROADMAKING 

hold  for  fast  traveling  automobiles;  that  is  always  clean; 
practically  noiseless;  free  from  dust  and  dirt;  non-absorbent 
of  heat;  must  be  comfortable  to  use  in  a  degree  denied  other 
pavements. 

The  preparation  of  the  surface  of  the  earth  for  the  laying 
of  the  pavement  is  no  different  from  the  preparation  required 
for  pavements  of  other  materials.  The  cross- 
Construe-  section  must  be  crowned,  the  crown  depending 
upon  the  grade  of  the  road  or  street  as  well  as  upon 
the  material.  For  concrete  roadways  the  crown  recommended 
is  that  used  for  stone. 

The  ground  should  be  formed  carefully  to  the  contour  of 
the  finished  surface  and  at  a  distance  below  this  surface 
equal  to  the  amount  required  by  the  specifications.  It  should 
be  carefully  excavated  and  all  soft  spots  should  be  dug  out 
and  refilled  with  good,  clean,  hard  material,  after  which  it 
should  be  alternately  sprinkled  and  rolled  until  a  wagon  with 
two-inch  tires  loaded  with  two  tons  of  material  can  be  drawn 
over  it  without  making  an  appreciable  indentation. 

The  foregoing  requirements  are  for  a  clay  or  heavy  soil, 
but  when  the  material  is  sandy  or  gravelly,  of  course  such 
hardness  in  the  rolled  surface  cannot  be  obtained.  The  dis- 
tance of  the  earth  surface  below  the  finished  surface  of  the 
roadway  likewise  depends  upon  the  character  of  the  soil  over 
which  the  road  will  go.  If  it  is  sandy  or  gravelly,  then  the 
concrete  can  rest  directly  upon  it.  If  it  is  clay  or  heavy 
soil,  there  should  be  at  least  three  inches  of  sand,  gravel, 
broken  stone,  or  hard  cinders  between  the  earth  and  the 
concrete.  This  cushion  coat  is  placed  to  minimize  the  danger 
from  frost. 

All  fills  in  the  sub-base  should  be  made  in  thin  layers  well 
moistened  and  rolled.  For  a  monolithic  pavement,  such  as 
concrete,  this  perfect  preparation  of  the  sub-base  is  of  great 
importance  and  extra  care  should  be  used. 

A  half-inch  board  should  be  set  on  edge  on  a  line  on  each 
side  of  the  street  about  three  or  four  feet  away  from  the 
edge  of  the  roadway;  about  where  the  edge  of  the  gutter 
would  be  if  the  gutter  were  constructed.  This  board  should 


CONCRETE  PAVEMENTS  389 

be  slightly  beveled  and  be  coated  heavily  with  oil  on  either 
side.  When  the  concrete  is  deposited  this  board  is  lifted 
and  the  space  should  be  poured  with  a  preparation  of 
asphalt  made  for  the  purpose.  This  joint  on  each  side  is  a 
longitudinal  expansion  joint  and  there  are  many  prepared 
fillers  for  expansion  joints  on  the  market.  A  good  one 
can  be  made  of  asphalt  mixed  with  coal  tar  from  which 
has  been  removed,  by  boiling,  all  moisture,  leaving  the 
pitch.  Coal  tar  alone  may  be  used  and  is  frequently  used 
for  this  purpose. 

An  expansion  joint,  to  be  such,  must  not  be  allowed  to 
fill  with  dirt  or  sand,  so  the  plastic  filling  is  a  necessity. 
Sheets  of  cork,  tar  and  sawdust,  tar  and  cork  dust,  as  well  as 
strips  of  tarred  paper  heavily  coated  with  cork,  have  all 
been  used  with  success.  At  intervals  of  about  fifty  feet 
there  should  be  similar  expansion  joints  laid  across  the  pave- 
ment. Although  there  has  been  some  discussion  over  the 
necessity  for  such  joints  in  concrete  pavements,  there  are 
many  such  pavements  in  use  and  so  far  none  have  been  con- 
structed without  expansion  joints. 

No  work  should  be  done  when  the  temperature,  either 
night  or  day,  falls  below  35°  Fahr. 

One  form  of  concrete  pavement  is  patented  under  the  name 
of  the  Hassam  pavement,  after  the  inventor.  After  the  road- 
way has  been  thoroughly  compacted,  it  is  covered 
with  broken  stone  to  a  depth  of  practically  the 
pavement  thickness  in  the  same  manner  as  that 
generally  specified  for  a  macadam  pavement,  and  the  stones 
are  so  graded  that  the  voids  are  reduced  to  a  minimum. 
After  the  stone  has  been  rolled  until  it  practically  ceases  to 
move  under  the  weight  of  the  roller,  a  thin  grout  composed 
of  Portland  cement,  one  part  and  sand  two  parts,  is  poured 
on  the  stone  until  the  voids  are  filled  and  the  grout  rises  to 
the  surface.  The  rolling  or  tamping  continues  during  the 
process  of  grouting.  Then  a  very  thin  layer  of  pea  gravel 
is  placed  all  over  the  surface  and  rolled  until  the  grout  flushes 
up  through  it. 

Another  form  of  concrete  pavement,  not  patented,  is  to  mix 


390  THE  ART  OF  ROADMAKING 

stone,  sand  and  cement  together  precisely  as  in  mixing  con- 
crete, but  no  water  is  added.  This  dry  material,  really  a 
macadam,  is  then  spread  over  the  surface  and  treated  as 
macadam  is  treated.  When  sprinkled  and  rolled,  of  course 
it  is  converted  into  regular  concrete,  but  as  it  has  consider- 
able solidity  before  wetting,  the  roadway  is  very  solid.  It 
has  been  used  greatly  as  ballast  for  surfacing  tracks  of  elec- 
tric roads  and  permits  of  good  work  being  done  in  this  way. 
The  track  can  be  perfectly  aligned  and  adjusted  and  then 
the  concrete  wetted  and  permitted  to  set  afterwards. 

The  best  way  to  make  a  concrete  roadway,  however,  is 
to  make  it  in  the  regular  way  by  depositing  layers  of  concrete 
until  the  desired  thickness  is  obtained,  and  then  finish  the 
surface  according  to  what  is  considered  best  for  that  par- 
ticular locality. 

Concrete  is  composed  of  sand  and  cement  mixed  together 
to  form  a  paste  and  with  some  aggregate  that 
will  combine  with  this  paste  to  make  a  good  stone. 
The  best  aggregate  is,  of  course,  stone. 

The  following  specifications  for  materials  for  Portland 
cement  sidewalks,  adopted  by  the  National  Association  of 
Cement  Users,  January  24,  1908,  serve  to  show  what  is  con- 
sidered good  practice  in  selecting  the  materials: 

"Sand  shall  pass  a  No.  4  screen  and  be  free  from  foreign 
matter,  excepting  loam  or  clay,  which  will  be  permitted  if 
the  quantity  does  not  exceed  five  per  cent,  and  when  these 
ingredients  do  not  occur  as  a  coating  on  the  sand  grains. 

"Not  more  than  40  per  cent  shall  be  retained  on  a  No. 
10  sieve,  or 

35  per  cent  pass  a  No.  10  and  be  retained  on  a  No.  20  sieve, 

20  per  cent  pass  a  No.  20  and  be  retained  on  a  No.  30  sieve, 

30  per  cent  pass  a  No.  10  and  be  retained  on  a  No.  40  sieve, 

40  per  cent  pass  a  No.  40  and  be  retained  on  a  No.  50  sieve. 

"Not  more  than  20  per  cent  shall  pass  a  No.  50  sieve,  or 

70  per  cent  pass  a  No.  10  and  be  retained  on  a  No.  40  sieve, 
70  per  cent  pass  a  No.  20  and  be  retained  on  a  No.  50  sieve. 

"Stone  shall  be  crushed  from  clean,  sound,  hard,  durable 


CONCRETE  PAVEMENTS  391 

rock,  be  screened  dry  through  a  f-inch  mesh,  and  be  retained 
on  a  J-inch  mesh. 

"  Screenings  from  the  crushed  stone  specified  above,  which 
shall  meet  the  requirements  for  sand,  may  be  substituted 
for  sand  if  so  approved. 

"  Gravel  shall  be  clean,  hard,  and  vary  in  sizes  from  that 
retained  on  a  J-inch  mesh  to  that  passed  by  a  |-inch  mesh. 

"Unscreened  gravel  shall  be  clean,  hard  and  contain  no 
particles  larger  than  f-inch.  The  proportions  of  fine  and 
coarse  particles  must  be  determined  and  corrected  to  agree 
with  the  requirements  for  concrete. 

"Water  shall  be  reasonably  clean,  free  from  oil,  sulphuric 
acid  and  strong  alkalies." 

In  the  foregoing  requirements  those  for  sand  are  first- 
class,  and  nothing  can  be  added.  In  regard  to  the  use  of 
stone  screenings  in  place  of  sand,  it  is  well  to  note  that  all 
dust  must  be  screened  out  and  the  screenings  used  should 
comply  with  the  specifications  for  sand  as  to  size  of  grains. 
The  dust  is  apt  to  ball  up  badly  and  prevent  a  good,  thorough 
mixing.  It  also  requires  more  water. 

The  unscreened  gravel  referred  to  means  ordinary  gravel 
as  this  term  in  understood  by  the  average  man.  As  an 
excess  of  sand  is  weakening  to  concrete  care  should  be  taken 
to  see  that  the  proportions  are  about  right  when  using  such 
ready  mixed  gravel.  It  is  always  best  to  screen  gravel  and 
remix  in  proper  proportions. 

The  caution  about  using  clean  water  is  a  good  one.  It  is 
a  common  practice  for  sidewalk  men  to  use  water  from  gutters 
and  drains  on  their  work  and  then  blame  the  cement  for 
failures. 

Wrhen  working  in  sections  of  the  country  where  there  is 
considerable  alkali  the  water  should  be  tested  and  should 
never  be  used  if  it  contains  alkali.  The  gravel  should  also 
be  tested  as  well  as  the  sand.  If  it  is  impossible  to  obtain 
other  material  within  a  reasonable  cost,  samples  of  the  water, 
sand  and  gravel  should  be  taken  to  a  competent  chemist  for 
analysis  in  order  to  see  whether  the  alkali  contained  is  likely 
to  be  harmful  to  the  concrete,  as  some  of  the  salts  known 
commonly  as  "alkali"  are  not  harmful. 


392  THE  ART  OF  ROADMAKING 

The  stone  used  for  concrete  roadways  can  be  slightly 
larger  than  specified,  but  should  not  exceed  one  and  one-quarter 
inches  in  the  largest  dimension  and  should  be  as  nearly  cubical 
in  shape  as  possible.  Rounded  gravel  packs  better  than 
broken  stone  and  occasionally  broken  stone  comes  from  a 
formation  that  is  rather  brittle  and  the  crusher  causes  small 
cracks  that  extend  throughout  the  stone  and  are  apt  to  be  a 
source  of  weakness. 

In  building  concrete  roadways,  however,  one  is  not  compelled 
to  use  stone  only.  Concrete  can  be  made  with  stone,  broken 
brick,  burnt  clay  ballast,  slag,  clinkers,  chats,  and,  in  fact, 
any  good  firm  material  that  is  able  to  stand  exposure  to  the 
weather  without  breaking  down,  that  will  not  melt  or  be  too 
readily  attacked  by  moisture  or  acids.  The  bed  of  the  pave- 
ment can  be  made  of  good  concrete  materials  and  the  topping 
or  surfacing  of  good  sand. 

The  standard  sidewalk  specifications  of  the  National  Asso- 
ciation of  Cement  Users  further  say: 

"The  concrete  for  the  base  shall  be  so  proportioned  that 
the  cement  shall  overfill  the  voids  in  the  sand  by  at  least 
five  per  cent  and  the  mortar  shall  overfill  the  voids  in  the 
stqne  or  gravel  by  at  least  ten  per  cent.  The  proportions 
shall  not  exceed  one  part  of  cement  to  eight  parts  of  the 
other  materials.  When  the  voids  are  not  determined  the 
concrete  shall  have  the  proportions  of  one  part  of  cement, 
three  parts  sand  or  screenings  and  five  parts  stone  or  gravel. 
A  sack  of  cement  (94  pounds)  shall  be  considered  to  have 
a  volume  of  one  cubic  foot. 

"To  determine  voids,  fill  a  vessel  with  sand  and  let  net 
weight  of  sand  equal  B.  Fill  same  vessel  with  water  and 
let  net  weight  of  water  equal  A. 

Per  cent  of  voids  =  100(2.65A- B)/2.65A 

"This  formula  may  also  be  used  in  determining  voids  in 
crushed  stone  and  screenings  by  substituting  for  2.65  the 
specific  gravity  of  the  stone." 

The  following  is  a  more  simple  method  for  determining 
voids  in  coarse  aggregates:  "Fill  a  vessel  with  the  aggre- 
gate and  let  net  weight  equal  B.  Add  water  slowly  until  it 


CONCRETE  PAVEMENTS  393 

just  appears  on  the  surface  and  weigh.     Let  net  weight  equal 
A .     Fill  the  same  vessel  with  water  and  let  net  weight  equal  C. 

Per  cent  of  voids  =  100(A-£)/C 

"Use   a  vessel   of   not   less   than   one-half   cu.ft.  capacity. 
The  larger  the  vessel  the  more  accurate  the  result." 

These  specifications  are  very  good,  but  the  men  who  do 
the  work  are  generally  opposed  to  all  the  weighing,  and  the 
formulas,  simple  as  the  calculations  are.  The  following 
method  is  recommended:  Make  a  box  two  feet 
wide,  five  feet  long  and  one  foot  deep  of  two-inch  € 
tongue  and  grooved  plank,  white  leaded  in  the 
seams  so  it  will  not  leak.  Fill  this  box  level  with  the  larger 
aggregate.  Then  pour  into  it  slowly  and  carefully  water 
from  cans  of  definite  size.  When  the  box  is  full  the  amount 
of  water  in  cubic  feet  represents  the  per  cent  of  voids  in 
the  stone,  because  the  box  contains  exactly  ten  cubic  feet. 
Empty  the  box  and  spread  the  stone  on  a  platform.  Measure 
out  sand  that  will  represent  the  voids  found  in  the  stone 
and  mix  the  sand  and  stone  together,  then  fill  the  box 
with  the  mixture.  After  this  is  leveled  off,  pour  in  water, 
carefully  measuring  it  as  it  goes  in,  and  the  amount  of 
water  will  represent  the  voids  in  both  stone  and  sand. 
If  this  does  not  exceed  ten  per  cent,  it  will  represent 
the  amount  of  cement  required,  but  if  it  exceeds  ten  per 
cent,  then  some  fine  sand  should  be  used  to  fill  part  of  the 
voids.  Density  is  wanted  and  the  most  dense  concrete  is 
obtained  when  the  materials  are  graded  in  size. 

It  does  not  do  to  go  to  too  much  expense  in  grading  the 
concrete   materials,    but   some   expense   should   be 
gone    to    in   this   regard    for   the    quality    of    the  Proportion- 
material    obtained   will    pay  for    the    extra    work,   materials. 
The    most    commonsense    method   of    ascertaining 
the    right    proportions    is    that    given    by  Wm.   B.   Fuller:* 
Use    a    piece   of    iron   pipe    about    ten    inches    in   diameter 

*  Taylor  and  Thompson,  "  Concrete." 


394  THE  ART  OF  ROADMAKING 

and  weigh  it  carefully.  Mix  some  concrete  in  the  propor- 
tions intended  for  use  on  the  work  and  tamp  it  into  this  pipe 
and  note  the  height  to  which  the  pipe  is  filled.  Weigh  the 
pipe  with  its  contents  and  throw  the  concrete  away  before 
it  sets.  Now  make  another  batch  with  the  same  amounts  of 
materials,  but  in  different  proportions.  Weigh  this  like  the 
first  one.  Make  a  number  of  batches  in  which  the  cement 
shall  be  one-eighth  of  the  mass,  but  in  which  the  sand  and 
stone  proportions  will  be  altered.  That  batch  in  which  the 
clyinder  is  filled  the  least,  and  which  weighs  the  most  per 
unit  of  volume  is  the  most  dense  concrete.  This  method  is 
sensible,  because  the  materials  at  hand  must  be  used  and 
no  expense  be  incurred  in  screening  and  separating  in  order 
to  make  exact  proportions.  By  proportioning  by  Mr.  Fuller's 
method,  a  1:2.5:5.5  mixture  may,  for  example,  be  used 
instead  of  a  1:3:5  mixture.  The  sand  may  be  coarse  or  be 
in  fact  a  very  fine  gravel  containing  considerable  sand;  in  which 
case  a  1:3.25:4.75  mixture  might  be  used. 

The  concrete  should  be  mixed  in  a  machine,  as  this  gives 
superior  concrete  at  a  much  less  cost  than  hand  mixing.  With 
batch  mixers,  each  batch  is  certain  to  contain  the 
exact  proportions  called  for  and  to  receive  the  right 
amount  of  turning.  There  are,  however,  a  number  of  con- 
stant delivery,  or  continuous,  mixers  that  can  be  safely  used, 
provided  a  constant  watch  is  kept  on  the  cement  feed.  This 
is  the  most  important  and  the  one  that  gives  the  most  trouble. 
Hand  mixture  for  concrete  roadways  can  be  done  more 
cheaply  than  the  hand-mixing  usually  called  for  in  building- 
work.  Two  steel  platforms,  twelve  feet  long  and  six  feet 
wide,  are  used,  which  are  turned  up  at  each  end  and  have  a 
heavy  plank  on  each  side,  so  they  resemble  in  appearance 
river  scows,  having  a  depth  of  one  foot.  Over  one  end  is 
spread  the  stone  in  the  number  of  inches  that  corresponds 
to  the  proportion  required  in  the  mixture.  Over  the  stone 
is  spread  the  sand  in  its  proportion.  Over  the  sand  is  spread 
the  cement.  Some  men  spread  the  sand  first  and  put  the  stone 
on  top,  then  cover  with  cement.  The  reason  is  that  they 
say  some  of  the  sand  will  sink  into  the  voids  in  the  stone  and 


CONCRETE  PAVEMENTS  395 

thus  more  sand  is  used  than  should  be.  If  the  sand  is  put 
down  first  the  stone  will  not  be  lost  in  it  and  as  the  cement 
is  measured  in  bags  anyhow  that  if  some  cement  goes  down 
into  the  voids  it  does  not  matter.  The  difference  is  not 
worth  wrangling  over. 

Say,  for  example,  the  mixture  is  1:3:5.  A  layer  five 
inches  deep  of  stone  will  be  spread  over  the  platform  and 
upon  that  will  be  spread  three  inches  of  sand.  One  inch  of 
cement  will  cover  it  evenly.  The  measuring  is  not  done  by 
guess,  but  by  boxes.  A  frame  of  wood  five  inches  high  and, 
say,  five  feet  square,  is  placed  on  the  platform  and  this  is 
filled  even  to  the  top.  Then  another  box,  the  same  size 
(without  a  bottom),  is  placed  on  it,  but  this  frame  has  a 
height  of  only  three  inches  instead  of  five.  This  is  filled 
with  sand,  after  which  the  frames  are  lifted  by  handles  at 
the  corners  and  the  stone  and  sand  spread.  The  cement  is 
determined  by  a  certain  number  of  bags  to  the  batch  and 
this  number  of  bags  is  placed  over  the  sand. 

When  this  is  done  the  frames  are  taken  to  the  next  plat- 
form alongside  the  first  and  the  same  process  followed.  On 
the  first  platform  are  standing  men  with  rubber  boots  and 
having  long-handled  hoes,  such  as  plasterers  use.  For  a 
platform  six  feet  wide  five  men  will  be  necessary.  As  soon 
as  the  material  has  been  smoothed,  these  men  commence 
with  their  hoes  to  pull  it  over  about  a  foot  at  a  time.  They 
take  a  slice  about  a  foot  wide  off  the  front  edge  and  pull  it 
ahead  about  two  feet,  then  take  another  foot  in  the  same 
manner  until  the  whole  mass  has  been  gone  over.  Then  they 
start  at  the  front  and  pull  it  again  in  the  same  way.  Three 
pullings  and  it  is  at  the  far  end  of  the  platform  when  they 
immediately  begin  to  pull  it  back.  This  time,  however, 
two  men  start  in  to  sprinkle  it  with  rose  nozzles  and  the 
three  times  the  mass  is  turned  it  is  turned  wet.  This  makes 
a  total  of  three  turnings  dry  and  three  turnings  wet.  By 
this  time  the  other  platform  is  ready  for  their  attention  and 
the  men  go  there  while  the  wheelbarrow  loaders  shovel  the 
mixed  concrete  into  wheelbarrows  from  one  end  of  the  plat- 
form while  another  batch  is  being  prepared  for  the  men  with 


396  THE   ART  OF  ROADMAKING 

the  hoes,  at  the  far  end.  Sometimes  it  is  possible  to  arrange 
these  mixing  platforms  so  the  concrete  can  be  thrown  directly 
into  place  without  using  wheelbarrows.  However,  it  does 
not  always  pay  to  substitute  shoveling  and  long  throwing 
for  wheelbarrow  work. 

The  usual  methods  of  hand  mixing  can  just  as  well  be 
followed,  of  course,  but  the  method  described  is  the  lowest 
in  cost  and  produces  excellent  results.  The  concrete  should 
be  very  quaky  and  in  fact  should  flow  readily,  but  should  not 
run  like  thin  milk.  It  should  be  like  a  sticky  heavy  cream. 

The  concrete  must  be  solid,  not  porous.  Tamping  or 
rolling  should  be  insisted  upon. 

The  topping  should  be  not  less  than  one  inch  thick.  Some- 
times it  is  two  inches  thick,  but  that  is  extravagant.  It 
should  be  put  in  place  within  thirty  minutes  after 

finfshhf  and  the  base  has  been  placed  if  P°ssible>  but  under  no 
circumstances  should  it  go  on  after  an  hour.     First 

spread  a  thin  mortar  coat  of  nearly  pure  cement  mortar 
over  the  base  to  the  depth  of  about  an  eighth  of  an  inch 
and  then  put  on  the  topping. 

The  topping  should  consist  of  pebbles  about  one-quarter 
of  an  inch  in  size.  The  voids  should  be  determined  and  one- 
half  the  voids  filled  with  material  about  an  eighth  of  an  inch 
in  size.  The  remainder  of  the  voids  should  be  filled  with 
clean,  coarse  sand.  This  mixture  composes  one-half  the 
topping,  the  other  half  being  cement.  Some  men  use  one 
and  one-half  parts  of  this  mixture  to  one  part  of  cement. 
Trial  had  best  be  made  by  the  party  doing  the  work,  for 
so  much  depends  upon  the  coarseness  of  the  materials.  Fine 
sand  is  usually  round  and  requires  more  cement. 

This  topping  is  floated  with  wood  floats,  as  steel  floats 
produce  too  smooth  a  surface.  It  is  cut  through  at  the  ex- 
pansion joints  and  lined  off  into  blocks  the  size  and  shape 
of  stone  paving  blocks.  The  cuts  over  the  expansion  joints 
in  the  base  are  filled  with  the  regular  expansion  joint  com- 
position. 

Sometimes  the  surface  is  not  floated  but  the  topping  is 
put  on  and  tamped  somewhat,  after  which  it  is  swept  with 


CONCRETE  PAVEMENTS  397 

a  very  coarse  broom.  Occasionally  we  see  the  surfaces 
treated  with  acid  to  eat  away  the  cement  before  it  is  fully 
set,  so  the  stones  will  appear  and  make  the  surface  rough 
for  foothold.  Sometimes  after  the  topping  is  on  and  before 
it  is  set,  a  covering  of  pea  gravel  is  put  on  and  rolled  in  with 
a  lawn  roller. 

When  the  surface  is  finished,  there  should  be  a  covering 
of  sand  or  straw  put  over  it  and  this  covering  should  be  kept 
wet  for  a  week,  after  which  it  is  taken  off  and  the  street  sur- 
face exposed  for  three  days  longer,  when  it  is  ready  to  be 
thrown  open  to  traffic.  Sometimes  no  covering  is  put  on 
and  sometimes  a  covering  or  burlap  is  used.  Each  method 
has  its  advocates  and  each  has  been  used  with  success. 

The  street  surface  should  be  wet  every  day,  and  if  possible, 
kept  pretty  wet  for  two  or  three  weeks  after  completion. 
When  a  very  fine  surface  is  placed  on  the  road  and  it  is 
blocked  off  to  imitate  paving  blocks  the  roadway  is  generally 
thrown  open  for  travel  within  eight  or  ten  days.  Sometimes 
one  week  is  considered  long  enough.  When  a  rough  surface 
is  made  it  is  usual  to  make  traffic  wait  longer. 

The  cost  of  such  roadways  is  less  than  the  cost  of  any 
other  pavement  used,  for  it  consists  of  just  about  the  thick- 
ness of  concrete  used  for  such  roads.  It  costs  just  a  little 
more  than  the  bare  concrete  used  for  the  foundations  of 
pavements  of  wood,  asphalt,  stone  or  brick,  and  the  cost  of 
the  topping  is  much  less  than  the  cost  of  these  wearing 
surfaces. 

Figures  on  cost  vary  greatly  in  different  sections  of  the 
country,  and  the  work  done  so  far  on  concrete  roadways  in 
the  United  States  has  been  generally  done  in  good-sized 
cities  by  experienced  contractors  with  trained  men.  Not 
much  work  of  this  kind  has  been  done  in  small  towns  by 
contractors  and  until  more  of  it  has  been  done  it  is  hardly 
right  to  publish  cost  data  on  the  work. 

In  spite  of  the  many  advantages  of  cement  roads  brought 
out  by  the  writers  of  these  papers  the  limited  experience  of 
engineers  in  this  form  of  road  has  shown  that  its  rigid  surface 
does  not  for  long  withstand  the  constant  blow  of  horses' 


398 


THE  ART  OF  ROADMAKING 


FIG.  209. — Preparing  the  Surface. 


FIG.  210.— The  Finished  Road  Surface. 
Experimental  Concrete  Cube  Roadway. 


CONCRETE  PAVEMENTS  399 

hoofs  and  the  action  of  the  iron  tire,  while  its  rigidity  also 
makes  it  injurious  to  horses. 

Figs.    209    and   210   illustrate  an    experimental  Road  surface 
road  surfacing  of  two-inch  concrete  cubes,  built  by  ° 
the  Highway  Commission  of  New  York  State.* 

A  trackway  constructed    of   concrete   blocks       j 
described  and  illustrated  in  Chapter  XXI.  wayt 

CONCRETE  FOUNDATIONS 

The  best  specification  is  the  one  adopted  by  the  National 
Cement  Users  Association  at  its  meeting  in  Cleveland  in 
January,  1909,  as  follows: 

SPECIFICATIONS  FOR  PROPORTIONING  INGREDIENTS  FOR  PORT- 
LAND CEMENT  CONCRETE  FOUNDATION  FOR  STREET 
PAVEMENTS. 

FINE  AGGREGATE  shall  consist  of  sand,  crushed  stone,  gravel, 
or  slag  varying  in  size,  passing  when  dry  through  a  screen 
with  openings  ^-in.  in  diameter;  shall  be  of  siliceous  material, 
clean,  coarse,  free  from  vegetable  loam  or  deleterious  matter 
and  not  more  than  6%  shall  pass  a  screen  having  100  meshes 
per  lin.  in. 

COARSE  AGGREGATE  shall  consist  of  crushed  stone,  gravel, 
brick  or  slag  which  is  retained  on  a  screen  having  openings 
-J-in.  in  diameter  and  pass  through  a  screen  having  openings 
3  in.  in  diameter;  shall  be  clean,  hard,  durable  and  free  from 
all  deleterious  materials. 

MORTAR  shall  be  made  with  fine  aggregate  as  above  specified, 
mixed  with  such  proportions  of  cement  as  will  over-fill  the 
voids  in  the  fine  aggregate  by  at  least  5%  of  such  voids. 

CONCRETE  shall  be  made  of  coarse  aggregate  mixed  with  such 
proportion  of  mortar  made  as  above  specified  in  sufficient 
quantity  to  over-fill  the  voids  in  the  coarse  aggregate  by  at 
least  10%. 

SURFACE. — In  the  case  of  brick  or  other  form  of  block  pave- 
ments, the  surface  of  the  concrete  shall  be  as  smooth  as 
practicable.  In  the  case  of  asphalt  or  bitulithic  or  other 
sheet  pavement,  the  foundation  shall  be  finished  as  rough  as 
practicable  in  order  that  the  plastic  surface  will  as  thoroughly 

*  Engineering  Xews,  March  3,  1910. 


400  THE  ART  OF  ROADMAKING 

as  practicable  unite  with  the  concrete  foundation  and  prevent 
slipping  or  separation  between  the  concrete  and  the  wearing 
surface. 

In  all  cases  the  general  contour  of  the  surface  of  the  con- 
crete shall  be  as  closely  as  practicable  parallel  to  and  the 
requisite  depth  below  the  surface  of  the  completed  pavement 
in  accordance  with  the  grades  established,  and  the  directions 
of  the  city  engineer. 

If  any  portion  of  the  concrete  when  tested  by  a  template 
or  a  straight-edge  6  ft.  in  length  shall  show  a  surface  more 
than  J  in.  above  or  ^  in.  below  the  grade  established  by  the 
city  engineer,  then  "the  high  places  in  such  concrete  shall  be 
picked  or  otherwise  brought  down  to  the  proper  grade  and  the 
low  places  shall  be  filled  to  the  proper  grade  with  fine  concrete. 

TEST  FOR  VOIDS.— To  determine  the  voids  in  the  "coarse 
aggregate"  or  "fine  aggregate,"  prepare  a  vessel,  the  cubical 
contents  of  which  is  exactly  1  cu.  ft.  (1728  cu.  ins.),  being 
smaller  at  the  top  than  at  the  bottom.  Fill  the  vessel  with 
the  aggregate  thoroughly  dried  "  coarse  "  or  "  fine  "  as  the  case 
may  be,  which  is  to  be  used.  Thoroughly  shake  or  jar  the 
vessel  containing  the  aggregate  until  it  is  compacted  as 
thoroughly  as  possible  and  the  vessel  is  level  full.  Then 
ascertain  the  net  weight  of  the  fine  aggregate  in  the  vessel, 
deduct  this  weight  from  166  (the  weight  of  a  1  foot  cube  of 
mineral  of  which  the  fine  aggregate  is  composed)  divide  the 
difference  thus  obtained  by  166.  The  result  is  the  percentage 
of  voids. 

The  advantage  of  this  specification  is  that  if  either  the  fine 
or  the  coarse  aggregate  furnished  is  of  uniform  size,  the 
contractor  will  be  required  to  use  enough  cement  to  fill  the 
then  large  proportion  of  voids  in  the  fine  aggregate  and  enough 
mortar  to  fill  the  then  large  percentage  of  voids  in  the  coarse 
aggregate.  On  the  other  hand,  if  materials  are  available 
which  will  produce  a  smaller  percentage  of  voids  in  either 
the  fine  aggregate  or  the  coarse  aggregate,  the  contractor 
can  figure  his  proposal  accordingly  and  the  city  get  the  benefit 
of  the  lower  cost  of  construction. 


CHAPTER  XIX 
THE    CLEANING    AND    SANITATION    OF    CITY    STREETS* 

STREET  CLEANING,  considered  as  a  problem  in  sanitation  call- 
ing for  engineering  skill,  is  of  comparatively  recent  develop- 
ment, both  in  Europe  and  America,  and  was  only 
rendered  possible  by  first  providing  some  manner  of  Earty  hi 
hard  surface  to  work  upon.  Rome  had  its  "  tribuni 
verum  intentium"  at  an  early  date — officials  who 
were  charged  with  the  care  and  cleaning  of  the  streets, 
markets,  temples,  baths,  and  other  public  places.  Ordinances 
were  framed,  and  more  or  less  severely  enforced,  forbidding 
the  throwing  of  any  manner  of  filth  into  the  river  or  into  the 
streets  of  Rome. 

For  some  centuries  after  Paris  was  paved  every  citizen 
was  compelled  to  repair  the  street  before  his  house  and  to 
clean  it  at  his  own  expense,  in  accordance  with  an  edict  of 
Philip  the  Bold,  issued  in  1285.  This  law  was  practically 
unobserved,  however,  and  in  the  fourteenth  century  the  streets 
of  Paris  are  described  as  being  in  a  horrible  condition.  Later 
laws  made  street  cleaning  compulsory,  for  nobles  as  well  as 
for  the  common  citizen,  and  in  1501  a  company  was  formed 
for  cleaning  streets  by  contract  with  individuals.  Street 
cleaning  at  public  expense,  in  Paris,  was  inaugurated  in  1609, 
and  the  sum  of  70,000  livres  was  appropriated  for  this  purpose 
from  the  public  fund.  In  1704  the  city  collected  300,000 
livres  for  cleaning  streets  and  maintaining  lamps. 

A  pig  figures  prominently  in  the  first  Parisian  ordinances 
forbidding  the  deliberate  dirtying  of  the  streets.  The  young 
King  Philip,  son  of  Louis  "the  Fat,"  was  killed  in  1131,  as  the 

*  Condensed  partly  from  Beckman's  "History  of  Inventions  and 
Discoveries"  (1846)  and  partly  from  "Modern  Methods  of  Street 
Cleaning"  (1909),  by  George  A.  Soper,  Ph.D.,  M.  Am.  Soc.  C.E. 

401 


402 


THE  ART  OF  ROADMAKING 


S     tuo 

3  .a 


THE  CLEANING  AND  SANITATION  OF  CITY  STREETS  403 

result  of  a  fall  from  his  horse  brought  about  by  a  pig  in  the 
streets.  As  a  consequence  of  this  accident  an  order  was 
issued  forbidding  swine  running  loose  on  the  streets  of  the  city; 
but  this  order  was  bitterly  opposed  by  the  monks  of  the  Abbey 
of  St.  Anthony,  who  resented  this  affront  to  the  charges  of 
their  patron  saint,  and  demanded  liberty  for  the  swine  to  go 
where  they  pleased.  After  some  time  spent  in  controversy, 
the  pigs  belonging  to  this  abbey  were  granted  a  special  dis- 
pensation and  permitted  to  wallow  at  will,  provided  that 
they  had  bells  attached  to  their  necks. 

Up  to  the  fourteenth  century,  in  Paris,  and  as  late  as 
1750  in  Edinburgh,  citizens  were  permitted  to  thro\v  from 
their  windows  into  the  streets  before  the  house,  any  manner 
of  slops,  provided  that  they  called  out  three  times  before  doing 
so.  This  privilege,  so  inconvenient  to  the  passer-by,  'was 
strictly  forbidden  in  Paris  in  1395,  and  from  this  time  may 
be  dated  the  first  introduction  into  that  city  of  sanitary  con- 
veniences. It  is  interesting  to  note  that  when  Columbus 
sailed  for  the  Indies,  the  palace  of  King  Ferdinand  of  Spain 
was  destitute  of  any  conveniences  of  this  nature. 

In  Germany  the  cleaning  of  streets  was  at  first  considered 
as  a  most  dishonorable  employment,  which  is  some  places 
was  assigned  to  the  Jews  and  to  the  servants  of  the  public 
executioner.  Up  to  the  beginning  of  the  seventeenth  century 
the  streets  of  Berlin  were  never  swept,  and  pigs  ran  at  large 
throughout  the  city.  In  1624  the  Elector  desired  the  council 
to  have  the  streets  cleaned,  but  the  council  replied  that  it 
was  impossible,  as  the  citizens  were  busy  on  their  farms.  The 
dirt  in  the  public  market  place  accumulated  to  such  an  ex- 
tent that  in  1671  a  law  was  passed  compelling  every  country- 
man to  take  out  of  the  city  one  load  of  dirt  every  time  he  came 
to  market.  Pig-sties  in  the  streets  were  common  until  1681, 
when  an  order  was  issued  forbidding  the  feeding  of  swine 
within  the  city  limits.  Large  puddles  of  filth  were,  however, 
allowed  to  collect,  even  before  the  doors  of  the  best  houses, 
and  in  the  summer  these  puddles  emitted  a  horrible  stench. 
Mr.  Beckman  remarks  of  this  city  that,  "  If  bronze  and  marble 
could  smell,  Blucher  and  Bulow,  Schwerin  and  Liethen,  and 


404 


THE  ART    OF  ROADMAKING 


(From  Soper's  "Modern  Methods  of  Street  Cleaning.'") 

FIG.  212. — The  Center  of  London  on  a  Holiday 


(From  Soper's  "Modern  Methods  of  Street  Cleaning.") 

FIG.  213. — London. — Orderly  Bin  and  Hand-carts  used  in  Street  Work  at 
Entrance  to  London  Bridge. 


THE  CLEANING  AND  SANITATION  OF  CITY  STREETS  405 

duck-winged  angels  and  two-headed  eagles  unnumerable, 
would  be  found  on  their  pedestals,  holding  their  noses  instead 
of  grasping  their  swords." 

These  filthy  labyrinths  which  for  centuries  passed  for 
highways  and  byways  in  foreign  cities  have  given  way  to 
broad,  handsome  streets,  and  congested  districts  which  thirty 
years  ago  were  a  reproach  to  civilization,  have  been  entirely 
eliminated.  In  place  of  over-concentration  of  population 
within  the  limits  of  military  fortifications,  the  great  con- 
tinental cities  now  cover  large,  roomy  areas  in  which  the 
needs  of  public  health  and  welfare  are  provided  for  as  nowhere 
else  in  the  world. 

The  sanitary  regeneration  which  European  cities  have 
experienced  within  the  last  half  century  has  had  no  counter- 
part in  America,  where  there  has  been  no  necessity  for  such 
revolutionary  changes.  American  cities  were  all  small  when 
the  world  began  to  learn  that  efficient  sanitation  was  an  in- 
dispensable feature  cf  every  municipality.  There  was  never 
such  overcrowding,  or  such  slums  to  clean,  no  such  foci  of  filth 
to  eliminate  in  the  United  States  as  existed  abroad  fifty  years 
ago.  In  1860  there  were  only  sixteen  cities  in  the  United 
States  with  a  population  of  50,000  or  more,  as  against  one 
hundred  and  forty-eight  in  Europe. 

The   significant    feature   of   municipal   growth    in   America 
as  compared  with  municipal  growth  in  Europe  has  been  less 
the    expansion    of    cities    already    large    than   the 
great   number  of  small   cities   which   have  sprung    Municipal 
into    existence.     Hundreds    of    these    cities    have    America, 
passed,  and  are  still  passing,  rapidly  through  periods 
of  infancy,  youth,  and  middle  age,  toward  a  maturity  which 
foreign  cities  had  reached  half  a  century  ago;  and  their  sanita- 
tion takes  place  as  they  grow. 

That  branch  of  scavenging  which  has  to  do  with  the  ques- 
tion of  street  cleaning  is  not  at  first  troublesome  to  the  young 
American  city.  The  streets  are  merely  highways  which  run 
from  one  town  to  another  and  the  houses  which  are  built 
upon  these  highways  are  few  and  far  between. 

In  course  of  time,  as  the  population  increases,  the   main 


406  THE  ART  OF  ROADMAKING 

highway  is  paralleled  and  intersected  by  cross  roads;  these 
again  are  crossed  and  recrossed  to  satisfy  the  growing  require- 
ments of  the  place.  Capacious  gutters  make  their  appear- 
ance on  one  or  both  sides  of  the  streets,  but,  except  for  an 
occasional  drain  to  some  brook  or  creek,  a  final  disposition 
of  surface  water  is  not  provided  for. 

The  first  important  public  sanitary  improvement  to  be  made 
in  the  village  is  a  public  water-supply.  The  subject  of  street 
paving  is  then  considered  and  some  macadam  is  laid  down. 
Means  are  sometimes  provided  in  summer  to  keep  down  the 
dust,  but  the  dirt  which  falls  upon  the  pavement  is  removed 
only  by  wind,  rain,  and  other  natural  agencies. 

A  sewage  system  is  installed  later  in  the  town's  growth, 
and  the  houses  are  gradually  built  closer  and  closer  to  one 
another  until  they  stand  in  immediate  contact.  More  atten- 
tion is  given  to  the  pavement  of  the  streets.  Macadam  is 
laid  and  sometimes  brick;  stone  and  asphalt  come  later. 
The  ditches  or  gutters  at  the  sides  of  the  streets  are  elimi- 
nated and  the  storm  water  is  collected  from  the  well-graded 
streets  through  catch-basins  into  the  sewers,  along  with  house 
sewage. 

The  streets  are  not  yet  systematically  cleaned.  Dirt  is 
often  allowed  to  collect  until  the  pavement  is  hidden  from 
sight.  Garbage  and  ashes  are  generally  removed  at  public 
expense  by  contract.  Sometimes  the  wastes  are  separated 
into  two  parts  by  the  householders  so  that  the  refuse  of  the 
kitchens  may  be  collected  separately  from  the  ashes  and 
other  wastes,  and  sometimes  all  the  wastes  are  collected  in 
one  receptacle. 

The  city  has  now  reached  its  period  of  adolescence — often 
one  of  high  mortality  due  to  the  absence  of  proper  sanitary  con- 
trol, and  fraught  with  many  dangers  to  the  future  of  the  place. 

The  period  of  maturity,  that  is,  the  period  in  which  civic 
responsibility  begins  to  express  itself  in  such  forms  as  the 
regulation  of  building  construction,  the  control  of  traffic, 
the  adoption  of  well-considered  plans  to  insure  public  health 
and  safety,  is  long  delayed.  The  paving  and  cleaning  of 
streets  and  the  collection  and  disposition  of  city  refuse  are  apt 


THE  CLEANING  AND  SANITATION  OF  CITY  STREETS  407 

to  be  the  last  matters  to  which  the  municipality  gives  itself 
proper  concern. 

In  appearance  and  use  the  city  street  is  in  strong  contrast 
with  the  rural  highway,  yet  the  street  always  remains  simply 
a  highway  in  the  public  regard.  The  houses  are  now  close 
together,  offering  a  solid  masonry  front  as  of  one  compact 
structure.  The  streets  are  paved  across  from  house  line  to 
house  line.  The  earth  has  disappeared  beneath  a  casing  of 
brick,  mortar,  ami  stone  which  is,  or  should  be,  impenetrable 
to  water.  The  pavements  should  also  be  treated  as  though 
they  were  impenetrable  to  man,  but  in  American  cities  they 
•are  being  constantly  broken  through.  They  are  torn  up 
with  little  or  no  regard  to  the  integrity  and  smoothness  of 
the  surface  and  with  the  sole  idea  of  reaching  the  pipes  and 
conduits  beneath.  The  integrity  of  the  surface  has  much  to 
do  with  the  cost  of  street  cleaning. 

As  the  city  grows  the  height  of  buildings  becomes  greater 
and  greater,  making  the  streets  relatively  narrower,  and  in- 
terfering with  free  access  of  air  and  sunlight;  it  leads  to  over- 
crowding of  the  sidewalks  and  carriageways. 

The  city  uses  its  streets  in  a  very  different  way  than  does 
the  village.  They  connect  every  household  and  are  not  only 
arteries  of  travel,  but  are  also  places  of  amuse- 
ment, health  resorts,  and  business  places  for  the  st^gtg 
people.  The  city  man  not  only  moves  through 
the  streets,  he  carries  the  dirt  of  the  street  into  his  home  on 
his  boots  and  clothing;  he  gets  his  food  and  air  through  the 
streets.  Unfortunately,  both  food  and  air  are  often  con- 
taminated with  the  product  of  the  ceaseless  wear  and  tear  of 
everything  perishable  in  the  city.  Ground  into  impalpable 
powder  and  raised  from  the  pavements  by  the  wind  this  city 
dust  hangs  in  the  atmosphere  and  can  plainly  be  seen  in  the 
air  like  a  haze  on  a  calm  day.  The  quantity  held  constantly 
in  suspension  is  so  great  that  it  affects  the  city's  climate; 
it  discolors  both  persons  and  their  clothing;  it  turns  marble 
and  even  granite,  yellow  and  black,  and  can  be  found  in  masses 
which  weigh  pounds  even  at  the  tops  of  the  highest  buildings 
of  New  York. 


408 


THE  ART  OF  ROADMAKING 


(From  Soper's  Modern  Methods  of  Street  Cleaning.") 
FIG.  214. — Westminster. — Orderly  with  Hand-cart. 


(From  Soper's  "Modern  Methods  of  Street  Cleaning.'") 

FIG.  215. — Westminster. — Sand   Bin   Filled   for   Use.     Street   Refuse   is 
Shovelled  into  a  Compartment  at  the  Top. 


THE  CLEANING  AND  SANITATION  OF  CITY  STREETS  409 


Of  all  the  many  sources  of  street  dirt,  the  greatest  amount 
which  becomes  scattered  over  the  street  pavement  originates 
from  vehicular  traffic.  The  ceaseless  movement  of  vehicles, 
with  their  horses,  contributes  materially  to  the  soiling  of  city 
streets.  The  transportation  of  sand,  coal,  hay,  manure,  and 


(From  Soper's  "Modern  Methods  of  Street  Cleaning."! 

FIG.  216. — Westminster. — Street-crossing  Sweeper  near  Houses  of  Parlia- 
ment. 

other  loose  material  in  poorly  constructed  and  overfull  wagons 
adds  to  the  quantity  of  refuse  in  the  streets,  and  in  the  average 
city  the  cleaning  department  itself  adds  materially 

to  the  work  which  it  has  to  do.     The   carts  are     ^ources.of 

street  dirt, 
generally    unsuitable    for   the    conveyance    of    the 

kind  and  quantity  of  refuse  they  have  to  carry.     In  conse- 


410 


THE  ART  OF  ROADMAKING 


quence,  dry  refuse  is  blown  from  the  carts   and  wet   refuse 
drips  from  them. 

Failure  to  collect  house  refuse  with  fiequency  and  regularity 
causes  it  to  be  cast  into  the  carriageways  by  the  people  and 
to  fall  upon  the  streets  from  overfull  receptacles.  It  com- 
monly happens  that  street-sweepers  brush  refuse  into  piles 
and  leave  it  there  for  many  hours  without  removing  it.  Traffic 


(From  Soper's  "Modern  Methods  of  Street  Cleaning.") 
FIG.  217. — Paris. — Street  Sprinkling  by  Hose. 

and  the  elements  pulverize  and  scatter  the  refuse  under  these 
circumstances  and  double  the  labor  necessary  to  collect  it. 

In  many  places  earth  from  country  roads  is  dropped  upon 
the  pavements  by  the  movements  of  vehicles.  The  opening 
of  pavements  to  reach  piping  and  other  underground  struc- 
tures is  an  important  source  of  street  dirt.  In  some  towns 
peddlers  and  push-cart  merchants  add  materially  to  the  dirty- 
ing of  city  streets.  Finally,  as  sources  of  street  dirt  may  be 
mentioned  the  improper  storing  of  sand  and  other  building 


THE  CLEANING  AND  SANITATION  OF  CITY  STREETS  411 

materials  and  the  sanding  of  paveme-nts  by  street-car  com- 
panies  and   street-cleaning   authorities. 

As  cities  grow  and  become  more  and  more  congested,  the 
need  and  difficulty  of  keeping  the  sidewalks  and  carriage- 
ways free  from  dust  and  litter  increase;  but  in  spite  of  praise- 
worthy efforts  here  and  there,  the  streets  of  but  few  cities 
are  kept  in  a  satisfactorily  clean  condition.  There  are  almost 
always  large  parts  of  even  the  cleanest  cities  which  are  very 
dirty. 

One  of  the  reasons  for  this  unsatisfactory  condition  of  city 
streets  lies  in  the  fact  that  the  business  of  keeping  a  city  clean 
is  rarely  understood  by  the  public  or  by  the  officials  in  charge 
of  the  streets.     In  American  cities  of  small  size  it  is  still  cus- 
tomary to   clean  most  of  the  streets  not  regularly  and  sys- 
tematically, but  spasmodically  and  ineffectively— 
often    only    when   the    conditions    become    so    bad  Reasons  for 
that  public  endurance  will  no  longer  tolerate  them.  streets 
The  persons  assigned  to  the  labor  are  often  recruited 
from  the  ranks  of  the  unemployed  and  are  likely  to  be  either 
incompetent  or  unwilling  to   do   a  fair  day's  work.     Some- 
times men  of  advanced  age,  inmates  of  poorhouses  and  even 
convicts,  are  put  upon  the  streets  to  clean  them.     Any  kind 
of  labor  seems  to  some  good  enough,  and  it  is  small  wonder 
that  the  results  are  so  often  unsatisfactory. 

The  aim  of  sanitation  is  to  get  control  of  wastes  as  soon 
as  possible  after  they  are  produced  and  maintain  this  con- 
trol until  they   are   permanently   disposed   of.     It 
is   both   easier   and   cheaper  to   collect   large   par-    sanitation 
tides  of  refuse  and  small  particles  when  present  in 
relatively  large  and  compact  masses,  than  to  allow  the  refuse 
to  be  broken  up  and  scattered  before  attempting  to  gain  pos- 
session of  it. 

In  order  to  facilitate  the  work  of  the  street-cleaning  depart- 
ment, and  insure  its  success,  cooperation  is  desirable  between 
those  city  departments  which  are  responsible 
for  the  paving  of  streets,  the  opening  of  pavements, 
the  regulation  of  traffic,  the  storing  of  building 
materials,  and  the  management  of  markets,  as  well  as  with 


412 


THE  ART  OF  ROADMAKING 


householders.  Effective  cooperation  of  this  kind  is  rare  in 
America,  but  in  Europe  all  these  matters,  and  more,  are  not 
uncommonly  attended  to  by  one  central  authority. 

The  city  waste  materials  may  be  divided  into  three  divisions : 


(From  Sopcr's  "Modern  Methods  of  Street  Cleaning.") 

FIG.  218.— Berlin. — Electrically-driven  Machine  for  Cleaning  Streets. — 
The  Highest  Development  which  Street-cleaning  Machines  have  thus 
far  Attained. 


(1)  sewage,  (2)  city  refuse,  (3)  trade  refuse.     The  city  refuse, 
of  which  the  city  should  provide  for  the  collection 
city'waste!     anc*  disposal,  *s  separable  into  six  classes: 

1.  Garbage — animal,  vegetable  and  food  waste 
from  kitchens,  markets,  slaughterhouses,  etc.,  principally 
water  and  putrescible  organic  matter. 


THE  CLEANING  AND  SANITATION  OF  CITY  STREETS  413 

2.  Ashes — steam  and  household. 

3.  Rubbish — paper,    wood,    rags,    metals,    bottles,    broken 
glass,  sweepings  from  buildings  and  miscellaneous  inorganic 
matter  from  houses  and  manufactories. 

4.  Street  sweepings — animal  manure,  pavement  dirt,  drop- 
pings from  carts,  materials  from  building  construction,  leaves, 


(From  Soper's  "Modern  Methods  of  Street  Cleaning.'") 

FIG.    219. — Charlottenburg,    near    Berlin. — Watering-cart    and    Rubber 
Squeegee  for  Cleansing  and  Drying  the  Streets.     June,   1909. 

and  other  waste  materials  collected  from  the  sidewalks  and 
roadways. 

5.  Dead  animals. 

6.  Snow — including  the  resulting  ice  and  slush. 

To  dispose  of  the  dirt  which  soils  the  streets,  two  general 
methods  exist:  It  must  be  picked  up  and  hauled  away  in 
carts  or  it  must  flow  with  water  into  the  sewers. 

In  some  cities,  notably  Paris,  the  sewers  have  been  built 
with  the  idea  of  carrying  off  all  the  street  dirt  that  can  reason- 


414 


THE  ART  OF  ROADMAKING 


(Courtesy  of  "  The  Engineering  Magazine.") 

FIG.  220.— Two-ton  Sprinkling  Wagon  used  in  Berlin.— Mann's  (English) 
Steam-driven  Street  Sprinkling  Wagon. 


THE  CLEANING  AND  SANITATION  OF  CITY  STREETS  415 

ably  be  emptied  into  them,  but  the  best  engineering  opinion 
is  that  a  city's  sewers  can,  and  should,  be  made  to  carry  off 
only  the  fine  dirt  from  the  streets;  the  large,  bulky,  heavy 
particles  must  be  removed  otherwise. 

Good  pavements  in  good  repair  are  indispensible  to  good 
work  in  street  cleaning. 

The  easiest  to  clean,  but  the  pavement  which  requires  the 
greatest   amount   of  attention,   is   asphalt.     Macadam  is  the 
most   expensive   pavement    of   all   to    keep    clean.  Comparative 
Wood-block  pavements   are   more   expensive   than  cleanliness 
asphalt  and  less  expensive  than  granite  block  to of  Pave~ 
keep    in    good    sanitary    condition.     Fine,    dusty m 
dirt  is  most  conspicuous  on  asphalt.     A  good  granite  pave- 
ment has  a  capacity  for  holding  a  considerable  quantity  of 
fine   dirt  in   its   small   irregularities  without    causing  the  re- 
mainder to  be  offensively  apparent  either  as  dust  or  mud. 

To  remove  large  particles  of  refuse  from  the  street  pave- 
ments, the  custom  both  in  Europe  and  America  is  to  employ 
handworkers.  Their  object  is  to  pick  up  papers,  Orderlies 
horse  droppings,  and  other  refuse  which  they  can 
easily  and  quickly  remove,  and  to  leave  the  pavement  without 
conspicuous  litter.  In  many  European  cities  these  workers 
are  boys;  in  America  they  are  often  old  men. 

The  refuse  thus  collected  is  put  into  barrels,  bags  or  hand- 
carts or  thrown  temporarily  into  bins  or  pits  situated  inside 
the  curbline.  In  American  cities  small  metal  barrels  are  car- 
ried through  the  streets  on  light  carriages  which  the  workman 
pushes  along  before  him. 

Although    the    hand-workers    are    usually    provided    with 
shovels,  iron  scrapers,  and  brooms,  and  in  some  cases  hand- 
propelled    sweeping-machines,    they    do    not    and     Machinery 
cannot  remove  all  the  dust  and  mud  which  it  is    employed 
desirable  to  remove  from  a  city  pavement.     This     in  street 
can  only  be  done  by  the  use  of  water.     Nor  can 
hand  workers  compete  with  horse  or  motor-propelled  rotary 
brooms  in  removing  large  amounts  of  dirt  from  the  pavements. 
Handwork  is  best  on  pavements  which  are  in  poor  repair. 
In  machine  work  the  secret  of  success  lies  in  having  unob- 


416 


THE  ART  OF  ROADMAKING 


structed  streets  and  good  pavements,  but  the  attempts  made 
to  use  sweeping-machines  are  often  decidedly  crude.  The 
brooms  are  not  always  preceded,  but  are  sometimes  actually 
followed,  by  sprinkling-carts.  Too  often  no  sprinkling  ac- 
companies the  sweeping,  the  result  being  that  dirt  is  raised 
through  the  air  in  clouds  of  dust  to  settle  again  upon  the 
pavements  and  in  the  houses.  Hand-sweeping  is  open  to 
the  same  objection,  for  when  sprinkling  is  done  by  persons 


(From  Soper's  "Modern  Methods  of  Street  Cleaning."} 

FIG.  221. — Hamburg. — Street  Cleaner  with  Apparatus  about  to  Empty  a 
Hand-cart  Full  of  Sweepings  into  a  Temporary  Storage  Pit  Beneath 
the  Sidewalk. 

in  connection  with  this  work,  it  is  often  perfunctory  and  in- 
effective. 

The  facility  with  which  street  dirt  may  be  removed  from 
pavements  and  carried  through  the  sewers  in  the  presence  of 
an  abundance  of  water  should  be  remembered  when  showers 
and  rainstorms  occur.  At  such  times  a  street-cleaning  force 
can,  with  hose  or  with  simple  rubber  hand  scrapers,  clean  an 
immense  amount  of  fine  refuse  from  asphalt  streets  by  way 
of  the  sewers  with  comparatively  little  expenditure  of  energy 


THE  CLEANING  AND  SANITATION  OF  CITY  STREETS  417 

and  of  water;  but  instead  of  taking  advantage  of  the  oppor- 
tunity, most  street-cleaners  seek  shelter  on  the  approach  of 
rain. 

One  of  the  most  efficient  ways  used  in  Europe  for  cleaning 
smooth  pavements,  such  as  asphalt,  is  by  means  of  abundant 
water,  speedily  followed  by  scraping  with  rubber  squeegees. 
In  this  case  the  dirt  is  first  lubricated,  then  scraped  away 
and  the  pavements  partially  dried  by  the  scraping.  Machine- 
scrapers  hauled  by  horses  are  widely  employed  in  Europe  to 
clean  asphalt  streets.  Where  the  amount  of  dirt  on  the  pave- 
ment is  large,  most  of  it  should  first  be  removed  by  brooms 
before  the  more  thorough  cleansing  with  water  begins.  One 
of  the  advantages  of  scraping  with  rubber  squeegees  is  that 
it  leaves  the  pavements  comparatively  dry. 

There  is  usually  a  lack  of  system  and  method  about  the 
whole  undertaking  of  street  cleaning  in  American  cities,  but 
in  European  cities  the  streets  are  well  cleaned  and  the  pave- 
ments are  kept  in  good  repair.  It  is  recognized  by  the  author- 
ities that  not  only  is  the  cost  of  cleaning  dependent  upon  the 
condition  of  the  pavements,  but  also  that  it  is  quite  impossible 
to  keep  bad  pavements  clean. 

It  is  usual  in  the  greatest  cities  for  the  heads  of  street  clean- 
ing departments  to  be  engineers  who  have  had  considerable 
experience  in  this  class  of  work,  as  the  cleaning 

and  removing  of  refuse  from  the  streets  is  recog-      Street 

,  e    *•     L    •  cleaning 

mzed   to   be   one   of   first   importance   among   mu-      authority 

nicipal   sanitary   undertakings   and   a   proper   per- 
formance of  the  work  of  managing  a  street-cleaning  depart- 
ment  is   considered   to   require   thorough  competence  and   a 
long  training. 

The  street-cleaning  department  is  often  a  branch  of  a  larger 
department  which  has  charge  of  the  construction  and  repair 
of  all  structures  between  the  house  lines. 

In  the  city  of  London  the  control  of  street  conditions  by 
the  central  authority  is  so  complete  that  it  includes  not  only 
street  cleaning  and  refuse  removal,  but  the  construction 
and  maintenance  of  sewers,  sidewalks,  pavements,  fire  hy- 
drants, public  comfort  stations,  subways  for  purposes  other 


418 


THE  ART  OF  ROADMAKING 


than  passenger  transportation,  lighting,  .the  removal  of  dan- 
gerous structures,  the  erection  of  scaffolds  for  building  pur- 
poses, and  even  the  care  of  public  clocks.  This  authority 
is  called  the  Public  Health  Department  and  the  work  is  done 
under  the  direction  of  an  engineer  of  high  standing.  In  other 
large  cities  the  control  of  various  matters  which  have  to  do 
with  the  condition  of  the  streets,  is  also  much  centralized. 


(From  Soper's  "Modern  Methods  of  Street  Cleaning.") 

FIG.  222. — Amsterdam. — Modern  Type  of  Metal  Dumping  Wagon  Fitted 
with  Crane  for  Raising  Heavy  Receptacles. 


That  the  great  cities  of  Europe  are  cleaner  than  the  great 
cities  of  America  is  due  largely  to  the  quality  of  the  labor  em- 
ployed; much  depends  upon  the  capacity  of  the  ultimate 
personal  unit.  In  Germany  the  streets  are  cleaned  by  Ger- 
mans; in  France  by  Frenchmen;  in  England  by  English- 
men; in  America  by  Italians,  Irishmen,  negroes  and  often 
by  persons  who  have  lost  caste  in  every  community. 

Considerable   difference   exists   in   different    cities   concern- 


THE  CLEANING  AND  SANITATION  OF  CITY  STREETS  419 

ing  the  organization  of  the  forces  engaged  in  cleaning  the 
streets,  particularly  as  to  the  number  of  men  em- 
ployed and  the  extent  to  which  military  discipline  Organiza- 
prevails  among  them.  In  German  cities  it  is  the  rule  for°eg 
to  employ  workmen  who  have  done  military  duty, 
and  in  most  places  none  but  men  of  good  physique  and  energy 
are  used.  In  some  other  countries  it  is  evident  that  much 
less  care  is  exercised  with  regard  to  the  physical  qualifica- 
tions of  the  workmen;  occasionally  men  can  be  seen  who 
t,re  superannuated  and  in  other  ways  incapable,  and  in  a 
few  small  places  on  the  continent  women  take  part  in  the 
work  of  street  cleaning.  In  all  cases  responsibility  is  assigned 
in  the  street  forces  very  much  as  in  military  organizations. 
At  the  head  is  a  superintendent  who  has  officers  under  him 
upon  whom  he  can  rely  for  a  prompt  and  competent  execu- 
tion of  his  orders.  These  officers  are  in  turn  above  foreman 
and  working  foremen  who  come  in  close  touch  with  the  actual 
work. 

In  the  cities  which  have  the  cleanest  streets  there  are 
usually  two  divisions  of  the  work  of  cleaning — day  and  night 
work.  The  efforts  in  the  daytime  are  usually  directed  chiefly 
toward  removing  refuse  which,  when  scattered  about,  make 
streets  appear  disordered  and  dirty.  The  work  of  more 
careful  cleansing  is  done  at  night.  This  consists  in  watering 
the  streets  and  then  either  sweeping  them  with  horse  brooms 
or  horse-propelled  squeegees,  or  flushing  them  with  a  stream 
from  a  hose  accompanied  by  work  with  hand  brooms  or 
squeegees. 

In  every  case  the  cleaning  begins  by  a  thorough  sprinkling 
cf  the  streets — in  some  cities  this  covers  the  sidewalks.  In 
Paris  the  preliminary  wetting  is  followed  by  sweeping  with 
a  lotary  broom  and  in  many  cases  by  squeegees  propelled 
by  horses.  Rotary  brooms,  and  rotary  or  fixed  rubber  squee- 
gees hauled  by  horses,  are  used  in  nearly  all  cities. 

In  Paris,  much  street  dirt  is  flushed  into  the  sewers,  which 
are  unprovided  with  catch  basins,  and  when  built  were  in- 
tended to  be  sufficiently  capacious  to  carry  off  all  the  refuse 
which  might  get  into  them.  In  other  cities  much  of  the 


420  THE  ART  OF  ROADMAKING 

finely  comminuted  street  refuse  goes  to  the  sewers  also,  but 
some  of  it  is  caught  by  catch  basins. 

The  custom  of  flushing  gutters  exists  generally  throughout 
Europe  in  cities  of  every  size,  but  Paris  makes  the  most  use 
of  it.  In  London  the  streets  are  flushed  every  night,  except 
when  the  weather  is  so  cold  that  ice  might  form. 


(From  Soper's  "Modern  Methods  of  Street  Cleaning.") 
FIG.  223. — Antwerp. — Sprinkler,  Sweeper,  and  Collector  for  Street  Dirt. 

As  the  methods  of  street  cleaning  differ  in  different  cities, 
so  there  is  great  diversity  among  the  types  of  apparatus  em- 
ployed.    Motor-propelled    water    wagons    of    large 
Flushing.  ...  .  .       T        . 

capacities  are  in  use  in   London  and   Berlin.     In 

Antwerp  there  is  a  machine  which  sprinkles  the  street,  sweeps 
it,  picks  up  the  refuse  and  carries  it  away.  Mechanical  sweepers, 


THE  CLEANING  AND  SANITATION  OF  CITY  STREETS  421 

however,  cannot  dispense  with  hand  labor.     Moreover,  they 
require  a  fairly  smooth  pavement  to  work  well. 

The  material  swept  from  the  streets  of  foreign  cities  is  some- 
times turned  to  advantage,  but  the  principal  object  is  under- 
stood to  be  to  get  it  out  of  the  way.  Theoretically  of  much 
value  as  a  fertilizer,  and  possibly  of  some  use  as  a  fuel,  the 
practical  difficulties  of  utilizing  its  useful  ingredients  are  too 
great  to  make  it  of  substantial  benefit. 

In  Paris,  the  refuse  from  the  streets  is,  as  far  as  practicable, 
swept  into  the  sewers  and  carried  with  house  drain- 
age to  farms  or  emptied  into  the  River  Seine  be- 
low  the  city.     Some  of  this  refuse  and  other  solid 
matters  which  are  carried  by  the  sewage  have  to  be  removed 
before  the  sewage  is  utilized. 

The  most  usual  wray  to  dispose  of  street  dirt  is  to  use  it  to 
raise  the  level  of  low-lying  land.  Some  difficulty  is  expe- 
rienced in  this  direction,  for  there  is  not  always  suitable  land 
to  be  filled.  Furthermore,  unless  the  refuse  contains  a  large 
amount  of  indestructible  matter,  such  as  sand,  it  is  not  gen- 
erally considered  wholly  suitable  for  this  purpose.  In  many 
instances,  where  transporation  is  cheap  because  of  special 
canal  or  river  facilities,  street  sweepings  are  barged  away  to 
the  country  with  ether  city  wastes. 

An  important  part  of  the  work  of  the  street-cleaning  de- 
partment is  the  removal  and  disposal  of  house  refuse.  It 
is  an  almost  universal  custom  to  collect  this 

refuse  in    a   mixed   condition,  but  the  component  Removal  of 

.        ,.—  •  •  i    household 

parts  of  the  mixture  vary  in  different   cities  and  refuse< 

at  different   seasons   of   the   year. 

More  or  less  sorting  of  refuse  is  done  nearly  everywhere 
and  in  some  places  to  an  extreme  limit.  In  Paris,  the  house- 
hold refuse  is  sorted  by  ragpickers  upon  the  sidewalks,  by 
men  and  women  in  the  carts  which  collect  the  refuse  from 
the  houses  and  at  depots  in  the  outskirts  of  the  city  where  the 
material  is  hauled. 

In  most  British  cities  house  refuse  is  thrown  by  the  house- 
holders into  private  pits  where  it  remains  for  periods  of  time 
ranging  from  a  few  days  to  several  months.  On  the  Con- 


422  THE  ART  OF  ROADMAKING 

tinent  portable  cans  and  boxes  are  more  often  used.  In  some 
instances  the  cleaning  department  furnishes  receptacles,  carry- 
ing them  away  from  the  houses  when  full  and  returning  them 
empty  after  they  have  been  cleaned  and  disinfected. 

In  Great  Britain  the  destruction  of  household  refuse  by 
burning  in  special  furnaces  was  begun  about  thirty  years  ago 
and  is  now  generally  considered  a  desirable  procedure  wherever 
it  can  be  followed. 

To  partly  offset  the  cost  of  burning  refuse,  efforts  are  usually 


(From  Super's  "Modern  Methods  of  Street  Cleaning.") 

FIG.  224. — Where  Street-cleaning  is  unknown. — Highway  between  Vollen- 
dam  and  Edam,  Holland. 

made  to  utilize  the  heat  produced  to  raise  steam  for  produc- 
ing electric  light,  to  pump  sewage  or  water,  to  operate  ma- 
chines, and  for  many  other  purposes.  The  residue  is  used 
for  such  purposes  as  the  making  of  concrete,  mortar,  bricks, 
and  asphalt  pavements. 

On  reviewing  the  different   subjects  thus  briefly   covered, 

a  number  of  points   which   go  far  to  account  for 

Lary'     good    results    should    be    particularly    mentioned. 

Most  of  these  points  have  a  general  application  to  American 

conditions. 


THE  CLEANING  AND  SANITATION  OF  CITY  STREETS  423 

1.  Centralization  of  responsibility  for  the  repair  and  clean- 
ing of  street  pavements  is  desirable. 

2.  A  competent  person  should  be  at  the  head  of  the  street- 
cleaning  department — preferably  an  engineer  experienced  in 
sanitary  work. 

3.  An  organization  somewhat  military  in  character  is  best. 
But  it  is  unnecessary  that  the  military  spirit  should  be  car- 
ried beyond  the  point  required  to  fix  responsibility  and  in- 
sure a  proper  execution  of  orders. 

4.  Good   pavements   in   good    repair   are   indispensable   to 
efficiency  and  economy  in  street  cleaning. 

5.  Asphalt  is  the  easiest  pavement  to  clean,  but  the  hardest 
to  keep  looking  well  because  it  will  not  hide  dirt. 

6.  It  is  possible  to  clean  streets  without  the  use  of  water, 
but  the  results  are  only  measurably  satisfactory  in  most  in- 
stances.    For  the  best  work  there  should  be  sufficient  water 
used  to  carry  off  the  finer  dust  by  the  use  of  water  from  a 
hose   preceded   by   thorough   lubrication  with   water  from   a 
sprinkling  cart. 

7.  Sewers  should  be  used  to  carry  away  all  street  refuse 
and  sand  which   can  be  put  into  them  without  obstructing 
them  or  adding  seriously  to  the  problems  connected  with  the 
disposal  of  the  sewage. 

8.  Economy  demands  that  refuse  be  removed  as  soon  as 
possible  after  it  is  produced  and  unnecessary  littering  pre- 
vented. 


CHAPTER   XX 
SIDEWALKS,  CURBS   AND   GUTTERS 

THE  term  sidewalk,  as  ordinarily  applied,  refers  to  the 
pavement  usually  placed  on  the  side  of  the  carriageway 
pavement.  Its  object  is  to  provide  a  serviceable  roadway 
for  pedestrians,  and  the  conditions  that  render  a  road  well 
adapted  to  its  purpose  are  very  much  the  same  as  those 
required  for  a  walk.  It  is  not  subject  to  the  effects  of  heavy 
loads  such  as  use  the  roadway,  but  the  destructive  action  of 
water  and  frost  is  the  same  in  either  case,  and  the  various 
questions  of  economics,  location,  width,  grade,  and  materials 
that  affect  the  roadway  must  also  have  careful  consideration 
in  connection  with  the  sidewalk. 

In  business  districts  the  sidewalk  usually  extends  from  the 
building  line  to  the  curb.  On  residence  streets,  however,  it 
is  not  so  important  to  use  this  full  width  and  there  is  a  choice 
of  location,  as  to  whether  it  be  brought  up  to  the  property 
line  and  the  curb,  or  a  distance  from  either  or  both  to  allow 
a  margin  of  grass  and  a  row  of  trees. 

The  width,  exclusive  of  any  space  occupied  by  grass  and 
shade  trees,  should  be  sufficient  to  comfortably  accommodate 
the  traffic.     On  business  streets  this  should  be  at 
least  one-third  the  width  of  the  carriageway,  and 
on   residential   streets,   from   4   to  6   feet  is  the  usual  width, 
except   where   the   streets   are  solidly  built   up   with  houses 
several  stories  high,   when  the  walk    should  be  8  or   10  feet 
wide,  or  in  case  the  walk  is  used  as  a  promenade  or  an  im- 
portant thoroughfare,  when  the  width  is  even  greater. 

There  should  be  a  surface-slope  from  the  property  to  the 
curb,   to   shed   water  toward    the   gutter,   varying 
f       from   1  inch  in  3  feet  to  1  inch  in  5  feet,  accord- 
ing  to    the  roughness  of   the    surface,  and   the   longitudinal 

424 


SIDEWALKS,  CURBS  AND  GUTTERS  425 

slope  should  conform,  as  nearly  as   practicable,  to  the   grade 
of  the  street. 

Thd  foundation  is  of  as  great  importance  as  in  roadways. 
Whatever  material  may  be  used  for  the  surface,  if  the 
foundation  is  weak  and  yielding  the  surface  will 
settle  irregularly  and  become  extremely  objectionable,  if  not 
dangerous,  to  pedestrians. 

The  principal  requirements  of  a  good  sidewalk  are: 

1.  Smoothness,  but  not  so  as  to  be  slippery. 

2.  Non-absorbent  of  water,  so  that  it  may  dry    Require- 

.,,,,,  ments  of  a 

rapidly  after  rain.  good  waikt 

3.  Not  easily  abraded. 

4.  Uniform  quality  throughout,  so  that  it  may  wear  evenly. 

5.  Must  neither  scab  nor  flake. 

6.  Durability. 

7.  Low  in  first  cost. 

Of  these  1,  2,  6  and  7  are  the  most  important. 

The    materials    most     generally    used    for    sidewalks     are: 
asphalt,   brick,   cement,   concrete,    cinders,   gravel, 
macadam,   stone  slabs    (natural  and  artificial),  tar 
concrete,  and  wood  planks. 

The  relative  order  of  these  materials  as  compared  with  the 
essential  requirements  is  as  follows: 

Smoothness:  Readiness  of  drying:  Durability: 

Asphalt  and  cement  Asphalt  and  cement  Brick 

Stone  slabs  Stone  slabs  Cement 

Brick  Brick  Stone  slabs 

Plank  Plank  Gravel  and  macadam 

Gravel  Macadam  Asphalt 

Macadam  Gravel  Plank 

Cost  varies  with  the  locality  and  the  form  of  construction 
so  that  it  is  impossible  to  give  their  rank  except  in  particular 
cases.  While  stone  slabs  have  been  most  common  in  the 
past,  cement  and  brick  are  now  the  most  used  materials,  the 
former  where  a  first-class  walk  is  desired  and  the  second  where 
cheapness  is  a  prime  requisite.  Roots  of  trees  damage  brick 
walks  much  less  than  those  made  of  cement. 

Of  the  natural  stone,  sandstone  is  most  extensively  used. 


426 


THE  ART  OF  ROADMAKING 


Sandstone. 


This  forms  an  excellent  paving  material,  standing  high  in  all 
the  necessary  qualifications  of  a  good  sidewalk.  It  is  found  in 
the  quarries  in  layers  of  from  one  inch  to  three  feet 
in  thickness,  and  is  used  in  all  sizes,  many  of  the 
slabs  used  for  flagging  in  New  York  being  20  feet  long,  15  feet 
wide  and  8  to  10  inches  thick,  while  blocks  from  25  to  60  feet 
long  are  often  lifted  from  the  bed.  A  walk  made  of  split 
flagstones  is  ordinarily  a  little  smoother  than  one  made  of 
brick,  but  is  not  so  smooth  as  a  cement  walk. 


v\\x -H'i '. v  -^/jfnSssL  '  ••••*; ^  S\\^\<f^svs>^>\xV/^W^^>^w>. T: • 


FIG.  225. — Section  of  Suburban  Street,  showing  Broken-stone  Roadway, 
Paved  Gutter,  Tile  Drain  and  Gravel  Walk. 


Granite 


Wood. 


Granite  is  also  extensively  employed;  it  is  durable,  but  is 
expensive  and  wears  slippery,  so  that   its  surface 
must  be  frequently  roughened  to  keep  it  in  a  safe 
condition. 

Wood  planks  have  long  been  used  for  sidewalks,  especially 
in  small  communities.  They  are  cheap,  but  not  durable, 
and  they  require  constant  repair  to  keep  them  from 
becoming  dangerous.  They  were  more  common  in 
earlier  days  when  the  cost  of  wood  was  low,  but  in  later  years, 
owing  to  its  increasing  cost  and  to  the  comparatively  low  cost 
of  brick  and  concrete,  board  walks  are  much  less  common  than 
formerly. 

Brick  sidewalks  are  very  common  and  when  well  made  are 

cheap  and  durable  and  make  an  excellent  footway 

for    residential  streets  or  for    the  business  streets 

of  smaller   towns.      They  consist   ordinarily   of    hard-burned 

building  brick  laid  upon  a  porous  bed  of  sand  or  cinders,  but 


SIDEWALKS,  CURBS  AND  GUTTERS 


427 


in  districts  where  the  travel  is  heavy,  the  bricks  are  set  on 
edge  and  the  joints  are  filled  with  cement  mortar.  The 
ordinary  building  brick  is,  however,  not  suitable,  as  it  soon 
wears  out  and  breaks;  hard-burned  paving  brick,  with  plane 
parallel  surfaces  and  sharp  right-angled  edges  should  be  used, 


r 

- 

i 

1 

i 

(a)  Longitudinal  Herring-bone  Method. 


(6)   Diagonal  Herring-bone  Method. 


(c)    Square-course  Method. 
FIG.  226. — Methods  of  Laying  Brick  Sidewalks. 

and  great  care  must  be  exercised  in  the  method  of  laying 
the  bricks  to  prevent  unevenness. 

Bricks  are  very  advantageously  and  extensively  used  for 
street  crossings  on  unpaved  streets  and  on  streets  paved  with 
stone  block,  in  the  former  case  to  provide  a  clean  crossing  for 
pedestrians  and  in  the  latter  to  provide  a  smooth  surface. 

" Brick  sidewalks  are  cheap,  fairly  smooth  and  not  slippery; 
and  if  made  of  hard  brick  are  dry  in  damp  weather  and  durable 


Of    THE 

UNIVERSITY 


428 


THE  ART  OF  ROADMAKING 


under  very  heavy  travel.     Their  defects   are:     (1)   they  are 

rough  in  comparison  with  asphalt;  cement  and  the  best  stone 

slabs;    (2)  they  are  untidy,  since  grass  and  weeds  are  likely 

to  grow  in  the  joints."  * 

Artificial    stone    is    extensively    used.     There    are    many 

varieties  manufactured  under  different  names  and  subject  to 
several  patents,  the  most  common  being  those 
known  as:  granolithic,  monolithic,  and  kosmocrete. 
When  well  made  and  placed  with  proper  drainage 

provision,  any  one  of  these  forms  a  durable,  inexpensive  and 

altogether  satisfactory  pavement. 

Gravel  is  largely  employed  for  walks  in  suburban  streets, 


Artificial 
stone. 


Gravel. 


FIG.  227. — Section  of  Park  Walk,  showing  Manner  of  Removing  Surface 

Water. 

country  roads,  parks  and  pleasure  grounds,  principally  because 
of  the  natural  harmony  of  its  color  with  such  surroundings 
and  because  of  the  informality  and  ease  of  its  appearance 
as  compared  with  asphalt  and  cement.  This  method 
of  construction  is  substantially  the  same  as  in  the 
case  of  gravel  roadway  pavements.  A  good  example  of  the 
adaptability  of  gravel  for  pathways  is  found  in  the  case  of 
Central  Park,  New  York,  where  they  are  laid  on  every  variety  of 
ground  from  level  and  smooth  to  rocky  and  precipitous,  winding 
along  rugged  hillsides;  gently  undulating  over  meadows  and 
lawns,  and  sometimes  expanding  into  broad  and  capacious 
promenades.  They  are  carried  over  and  under  roads,  and 
over  brooks,  by  archways  and  bridges  of  various  kinds, 


*  Baker,  "Roads  and  Pavements,"  page  602. 


SIDEWALKS,  CURBS  AND  GUTTERS 


429 


ornamental  and  rustic ;  through  rough  gorges  and  ravines,  and 
along  the  water  edge  of  lakes  and  ponds.  They  are  made  in 
various  widths  from  3^  to  35  feet,  and  adapted  to  nearly 
every  circumstance  of  position,  locality,  use,  and  convenience 
that  ordinarily  occurs  in  walks  for  rural  or  park  purposes. 


(Copyright,  1909,  by  The  Chas.  H.  Elliott  Co.) 
FIG.  228. — Cinder  Path,  Lehigh  University  Campus,  So.  Bethlehem,  Pa. 

The  principal  causes  of  the  deterioration  of  this  kind  of 
walk,  and  the  greatest  source  of  trouble  and  expense  in  repairs, 
is  the  wash  from  water  brought  from  the  adjoining  slopes. 
Sometimes  a  single  shower  will  cause  damage  that  will  involve 
a  heavy  expense  for  repairs,  so  the  necessity  of  liberal  and 
ample  provision  to  guard  against  this  trouble  will  be  seen  to 
be  warranted  by  sound  economy. 


430 


THE  ART  OF  ROADMAKING 


Cement  and 
concrete. 


The  most  permanent  form  of  sidewalk  and  the  form  that  is 
daily  growing  in  favor  is  of  Portland  cement  construction. 
The  Portland  cement  concrete  sidewalk,  when 
properly  constructed,  meets  all  the  requirements 
of  evenness,  solidity  and  permanency,  and  in  prac- 
tically all  localities,  can  be  built  at  a  comparatively  low  cost. 
The  possibilities  of  concrete  are  well  appreciated,  but  often, 
through  lack  of  knowledge  of  the  material  and  inexperience 
in  handling  it,  many  walks  are  built  which,  sooner  or  later, 
become  more  or  less  defective. 

There  are  certain  rules  which  should  be  observed  in  all  cases, 
and  in  some  cases  additional  precautions  are  necessary.     The 


(a)  Improper  Construction.  (6)  Proper  Construction. 

FIG.  229. — Method  of  Constructing  Driveway  Across  Walk. 

location  of  a  walk  is  determined  regardless  of  the  natural 
fitness  of  the  foundation,  the  soil  and  drainage  conditions,  and 
it  is  important,  therefore,  that  these  matters  be  carefully 
studied;  materials  available  should  also  receive  careful  atten- 
tion, their  selection  being  made  with  reference  to  quality 
rather  than  with  reference  to  cost.  Weather  conditions 
seriously  affect  the  behavior  of  concrete  and  must  be  taken 
into  account  to  assure  permanence  of  the  walk.  Poor  work- 
manship, which  includes  improper  proportioning  of  materials, 
the  placing  of  a  walk  on  an  improperly  prepared  foundation 
and  failure  to  take  into  account  weather  conditions,  is  respon- 
sible for  practically  all  failures  that  occur.  Very  few  cement 
walks,  if  any,  have  been  worn  out. 

Cement  sidewalks  are  usually  made  of  cement  stone  slabs 


SIDEWALKS,  CURBS  AND  GUTTERS  431 

framed  in  place  on  the  job.*  To  accomplish  permanency, 
it  is  necessary  that  these  slabs  remain  hard,  tough  and  in  the 
original  position,  and  to  achieve  this,  methods  of  manu- 
facture must  be  employed  which  will  avoid  settlement  cracks, 
upheaval  by  frost,  crumbling  due  to  work  done  in  freezing 
weather,  contraction  and  expansion  cracks,  separation  of 
top  from  base,  and  disintegration. 

A  great  many  walks  have  slabs  warped  into  saucer-like 
shapes,  without  any  signs  of  cracking,  which  slabs,  unless 
the  walk  is  on  a  grade,  act  as  basins  holding  water  after  each 
rain.  These  warped  slabs  occur  both  in  walks  of  large  area 
made  up  of  a  number  of  rows  and  in  single  slab  suburban 
walks  flanked  by  lawns.  In  the  latter  case  there  is,  in  addition, 
usually  a  longitudinal  crack  along  the  center  of  the  walk,  as 
shown  in  Fig.  230.  Suburban  walks  flanked  on  one  side  by  a 
terrace  are  generally  the  worst.  A  great  many  walks  are 
cracked  at  curved  corner  curbs,  and  at  the  ends  of  walks 
next  to  the  curb  at  cross  streets;  often  slabs  in  the  middle  of 
long  walks  buckle  up,  as  shown  in  Fig.  231.  In  many  cases 
the  expansion  in  the  cement  walk  has  either  pushed  the  curb 
out  of  line  or  broken  it  off  entirely. 

In  concrete  walks,  as  usually  built,  the  earth  is  excavated 
to  10  or  12  inches  below  the  finished  surface  and  6  or  8  inches 
of  cinders  are  laid  for  foundations  on  which  the  3-inch  concrete 
walk  is  laid,  with  a  1-inch  cement  covering  surface.  When 
no  additional  drainage  is  provided,  water  enters  the  foundation 
of  the  walk  through  the  lawns  on  either  side,  and  at  all  the 
joints  between  the  slabs.  Naturally,  this  moisture  is  greatest 
at  the  sides  and  near  the  joints,  where  its  enters,  very  little 
reaching  the  center  of  the  slab.  Subsequent  freezing  causes 
greater  upheaval  of  the  foundation  near  the  edges  of  the  slab 
than  at  the  suspended  center,  and  the  slab  finding  bearing  only 
on  the  edges,  acts  as  a  beam.  The  load,  while  not  great,  is 
applied  continuously  and  simultaneously,  with  changes  in 

*  Correct  methods  of  construction  are  available  in  the  form  of  trade 
pamphlets  issued  for  gratuitous  distribution  by  several  of  the  leading 
cement  companies,  and  there  are  also  several  cheap  books  devoted  ex- 
clusively to  this  subject.  (See  Bibliography,  Appendix  V.) 


432 


THE  ART  OF  ROADMAKING 


SIDEWALKS,  CURBS  AND  GUTTERS 


433 


temperature,  and  finally  causes  a  flow  of  the  material,  resulting 
in  depression  and  permanent  set. 

The  dissimilarity  in  density  of  the  concrete  base  and  the 
top  coat  or  wearing  surface,  which  causes  a  different  ratio  of 


*>    ^ 

! 

"T" 

-I, 

' 

*"*" 

-  *f^?//7 

JL. 

E 

Plan 

i 

SS^-" 

,-....•/•••'•    --Cinders 
''•Broken  Stone 


Longitudinal 

Section 

A-B. 


ENG. 

NEWS. 


Transverse      Section. 
FIG.  231.— Details  of  Drains  for  Concrete  Sidewalks. 

expansion  and  contraction  in  the  base  from  that  in  the  top, 
also  results  in  warping. 

To   avoid  this  sagging  and  upheaval,   perfect  drainage  in 
the  sub-foundation  is  of  utmost  importance.     Fig.  231  repre- 
sents a  walk  in  which  drainage  is  taken  care  of  by 
trenches  about  10  inches  deep  and  of  a  convenient  Sub-founda- 
width  across  the  sidewalk,  extended  to  the  curb, 
and  filled  with  broken  stone.     The  ditches  are  dug 
across  obliquely,  so  as  to  take  advantage  of  the  slope  of  the 


434 


THE  ART  OF  ROADMAKING 


-3 


SIDEWALKS,  CURBS  AND  GUTTERS 


435 


sidewalk.  Fig.  233  shows  a  section  of  concrete  walk  as  specified 
by  the  city  of  Pittsburg,  which  provides  an  outlet  for  drainage 
to  the  curb  somewhat  like  that  on  Fig.  231. 

Upheaval   by   tree   roots   can   very   easily   be   avoided   by 
cutting  out   any  roots  which  will  run  under  the 

pavement  less  than  a  depth  of  six  inches  under    p  eav<*1  by 

r.  tree  roots. 

bottom  of  drainage  foundation. 

Broken  stone  and  gravel  are  sometimes  used  for  foundation, 
but  cinders  are  most  frequently  used  and  are  preferable. 
The  thickness  of  the  cinder  foundation  required 
varies  in  the  different  city  specifications  from  4 
to  12  inches.  A  thickness  of  6  inches  is  ample.  A  greater 
thickness,  unless  deep  enough  to  go  below  the  freezing  line, 


Foundation. 


/  Wearing 
Surface  •• 


.•-3  Portland  Cement, 
/  Concrete 


ENS. 

NEWS. 


<* 

'-Broken  Stone  ''6  Coarse  Cinder 

Drain  every  25  or  Broken  Stone 


FIG.  233. — Suggested  Design  for  Concrete  Sidewalk. 

would  really  be  detrimental,  as  the  upheaval  of  frozen  cinders 
would  be  proportional  to  its  thickness.  Cinders  that  have 
been  placed  in  a  walk  for  some  time  before  placing  the  cement 
should  be  picked  loose  and  retamped  so  that  the  entire  mass 
has  even  compaction.  If  some  places  are  packed  harder 
than  others,  the  flag  will  not  have  an  even  bearing  and  may 
break.  One  of  the  causes  of  inferior  concrete  in  the  base  is 
the  absorption  of  water  from  the  mixture  by  the  porous  founda- 
tion before  it  has  set;  therefore,  a  thorough  wetting  of  the 
foundation  just  before  placing  the  concrete  is  desirable. 

The  concrete  in  the  base  of  concrete  walks  is  generally 
the  most  inferior  concrete  made.  The  capital  and  equipment 
necessary  for  doing  this  kind  of  work  is  comparatively  small, 
and  the  construction  work  apparently  easy,  the  result  being 


436 


THE    ART    OF    ROADMAKING 


Groover. 


Finishing  Trowel. 


Roller. 


Blade  for  Cutting  Concrete  Base. 


Edger.  Rammer. 

FIG.  234. — Tools  used  in  Construction  of  Concrete  Sidewalks. 


SIDEWALKS,  CURBS  AND  GUTTERS  437 

that   many   walks   are  put   down  by   inexperienced    contrac- 
tors and  competition  has  reduced  the  price  so  that 
good  work   cannot  be  done  profitably.     But  even 
with  as  good  material  and  workmanship,  it  is  hardly 
possible  to  get  as  good  concrete  in  cement  sidewalk  base  as  in 
structures  of  larger  volume,  such  as  retaining  walls,  abutments, 
etc.,  as  in  tamping  a  thin  layer  of  concrete  laid  on  a  cinder 
bed,  the  concrete  may  compact  a  little  under  each  blow,  but 
a  great  part  of  the  force  is  expended  in  forcing  the  concrete 
up  at  another  place  and  possibly  dislodging  the  cinder  bed. 
This  is  one  of  the  reason^  why  it  is  necessary  to  have  the  cinder 
bed  thoroughly  compacted  before  placing  concrete,  and  why 
it   is   advisable  to  so  mix  the  concrete  and  have  it  of  such 
constituency  as  to  reduce  the  amount  of  tamping  necessary. 

Insufficient  water  is  often  used  in  mixtures  for  concrete 
base.  More  water  should  be  used,  and  thorough  mixing 
adhered  to,  as  well-mixed  concrete  is  more  dense  than  poorly- 
mixed  and  requires  less  tamping. 

A  great  many  failures  are  due  to  a  lack  of  bond  between 
the  top  coat  or  wearing  surface  and  the  concrete  base.     In 
the  laying  of  the  walk,  and  in  order  to  accomplish 
much  work,  the  concrete  base  is  sometimes  allowed 
to  get  its  initial  set  before  applying  the  top  coat,  consequently 
there  is  little  bond,  the  upper  wearing  surface  becomes  loose 
and  easily  breaks.     If  the  upper  surface  of  the  base  is  troweled 
or  smoothed  off,  the  strength  of  the  bond  is  reduced;    it  is 
important,  therefore,  to  leave  the  base  free  of  troweling. 

When  concrete  walks  were  first  laid,  forms  defining  the 
blocks  were  used  and  the  concrete  placed  in  alternate  blocks. 
When  these  had  set  the  remaining  spaces  were 
filled  in.  This  scheme  made  positive  joints  and  J01 
prevented  breaking  of  flags  on  account  of  settlement.  While 
this  is  still  required  in  some  specifications  the  greater  proportion 
of  work  is  done  in  continuous  sheets,  the  walk  being  cut  at 
the  joints  by  a  knife  and  sledge.  Some  specifications  require 
the  joint  to  be  filled  with  sand  and  the  surrounding  concrete 
tamped,  and  others  require  tar  paper  put  into  joint.  After 
the  top  coat  or  wearing  surface  is  put  on,  it  is  cut  through 


438 


THE  ART  OF  ROADMAKING 


FIG.  235. — Curb  Broken  Away  by  Expansion,  showing  Necessity  of 
Expansion  Joints. 


FIG.  236.— A  Miserable  Piece  of  Sidewalk  Construction. 

Apparently  every  rule  and  precaution  necessary  for  the  production  of  first-class 
work  was  disregarded  in  the  placing  of  this  walk.  The  fill  was  insufficiently  and 
improperly  prepared  and  was  not  protected.  The  base  was  weak,  failing  to  support 
the  top,  which  was  not  bonded  to  the  base.  This  is  an  extreme  example  of  shoddy 
construction. 


SIDEWALKS,  CURBS  AND  GUTTERS  439 

over  the  joint  in  the  base.  The  cutting  is  often  indifferently 
done  and  sometimes  the  cut  through  the  wearing  surface  is 
not  directly  over  the  cut  through  the  base.  Then  if  there 
is  any  settlement  the  top  will  crack  in  an  irregular  line.  Water 
will  also  get  in  at  the  joint  under  the  top  coat  and  freeze, 
causing  it  to  break.  The  objections  to  laying  the  alternate 
blocks  in  a  walk  are  that  it  is  hard  to  get  the  different  blocks 
in  a  true  plane,  the  appearance,  therefore,  is  not  so  good. 
Another  objection  is  the  increased  cost  and  time  required. 
It  would  seem  that  the  method  now  most  generally  followed  of 
building  a  continuous  course  and  cutting  up  into  blocks  with 
a  tool  designed  for  that  purpose  is  the  best.  The  tool  should 
be  so  shaped  as  to  make  the  top  edges  of  the  groove  firm, 
smooth  and  slightly  round,  and  should  be  long  enough  to 
cut  entirely  through  the  top  coat  and  the  concrete  base. 

The  greatest  failures  are  from  expansion,  and  to  take  care 
of  this  it  is  well,  in  addition  to  the  block  joints,  to  provide 
extra  joints  from  1  to  1J  inches  wide  about  every  100  feet  of 
walk  when  more  than  this  distance  is  laid  at  one  time;  also  at 
the  ends  of  walks  next  to  the  curb  at  cross  streets  and  along 
the  curb  where  the  sidewalks  are  very  wide  and  have  curved 
curb  corners.  These  joints  are  usually  filled  with  sand. 
It  is  not  necessary  or  desirable  to  have  sharp  sand ;  sand  with 
rounded  grains  will  answer  better.  Pitch  and  asphalt  have 
also  been  used  for  the  large  joints  and  will  prevent  to  some 
extent  moisture  reaching  the  cinder  bed. 

The  size  of  the  blocks  should  be  limited  to  about  6X6  feet. 
When  the  sidewalk  extends  from  a  building  to  the  curb  or 
in  subways  from  the  abutment  to  the  curb  or  curb  wall,  as 
the  case  may  be,  the  cement  walk  'should  not  be  built  tight 
around  the  building,  abutment,  curb  or  curb  wall,  but  an 
open  joint  about  1  inch  wide  should  be  left.  There  is  likely 
to  be  some  settlement  in  either  the  building,  abutment,  curb, 
curb  wall  or  sidewalk  and  irregular  cracks  will  result. 

Some  cracking  is  caused  by  the  upper  surface  of  the  walk 
drying  out  faster  than  the  bottom,  acting  very  much  as  dried 
mud  in  a  river  bottom,  where  the  sun  dries  the  top  first,  which 
shrinks  and  breaks  up  into  small  blocks.  Subsequent  shrink- 


440 


THE  ART  OF  ROADMAKING 


FIG.  237. — Section  of  Walk  showing  Careless  Construction. 


FIG.  238. — Snowing  Change  of  Grade. 

The  comfort  of  pedestrians  demands  that  the  grade  in  a  walk  shall  not  change 
suddenly  excepting  where  steps  are  advisable. 


SIDEWALKS,  CURBS  AND  GUTTERS  441 

ing  in  the  lower  stratum  only  increases  the  width  of  the  cracks. 
For  this  reason,  it  will  be  well  to  keep  the  top  of  the  walk 
moist  for  several  days  during  dry  weather.  It  is  known 
that  wetting  the  surface  will  also  produce  a  whiter  walk  than 
one  that  is  allowed  to  dry  out  quickly. 

Portland  cement  concrete  sidewalks,  when  properly  con- 
structed, are  no  doubt  superior  to  all  others.  The  cost  of 
construction  is  not  much  greater  than  other  sidewalks,  so 
that  their  more  extended  use  depends  upon  their  permanency. 
It  is  advisable,  therefore,  that  the  best  material  and  work- 
manship be  used  so  as  to  get  best  possible  results. 


STANDARD  SPECIFICATIONS  FOR  PORTLAND  CEMENT  CON- 
CRETE SIDEWALKS  OF  THE  NATIONAL  ASSOCIATION 
OF  CEMENT  USERS 

MATERIALS. — The  cement  shall  meet  the  requirements  of  the  specifica- 
tions for  Portland  cement  of  the  American  Society  for  Testing  Materials, 
and  adopted  by  this  Association  (Specification  No.  1),  January,  1906. 

AGGREGATES. — Fine  Aggregate  shall  consist  of  sand,  crushed  stone,  or 
gravel  screenings,  graded  from  fine  to  coarse,  passing  when  dry  a  screen 
having  j-inch  diameter  holes,  shall  be  preferably  of  silicious  materials, 
clean,  coarse,  free  from  vegetable  loam  or  other  deleterious  matter,  and 
not  more  than  6  per  cent  shall  pass  a  sieve  having  100  meshes  per  linear 
inch. 

Mortars  composed  of  one  part  Portland  cement  and  three  parts  fine 
aggregate  by  weight  when  made  into  briquets  shall  show  a  tensile 
strength  of  at  least  70  per  cent  of  the  strength  of  1 :  3  mortar  of  the 
same  consistency  made  with  the  same  cement  and  standard  Ottawa 
sand. 

Coarse  aggregate  shall  consist  of  inert  material,  graded  in  a  size,  such 
as  crushed  stone  or  gravel,  which  is  retained  on  a  screen  having  |-inch 
diameter  holes,  shall  be  clean,  hard,  durable,  and  free  from  all  deleterious 
materials.  Aggregates  containing  soft,  flat  or  elongated  particles  shall 
be  excluded. 

The  maximum  size  of  the  coarse  aggregate  shall  be  such  that  it  will  not 
separate  from  the  mortar  in  laying  and  will  not  prevent  the  concrete 
fully  filling  all  parts  of  the  forms.  The  size  of  the  coarse  aggregate  shall 
be  such  as  to  pass  a  1^-inch  ring. 

Water  shall  be  clean,  free  from  oil,  acid,  strong  alkalies,  or  vegetable 
matter. 

FORMS. — Forms  shall  be  free  from  warp,  and  of  sufficient  strength 
to  resist  springing  out  of  shape.  All  mortar  and  dirt  shall  be  removed 
from  forms  that  have  been  previously  used. 

The  forms  shall  be  well  staked  to  the  established  lines  and  grades,  and 
their  upper  edges  shall  conform  with  finished  grade  of  the  walk,  which 
shall  have  sufficient  rise  from  the  curb  to  provide  proper  drainage;  but 
this  rise  shall  not  exceed  f  inch  per  foot,  except  where  such  rise  shall 
parallel  the  length  of  the  walk. 


442  THE  ART  OF  ROADMAKING 

All  forms  shall  be  thoroughly  wetted  before  any  material  is  deposited 
against  them. 

SIZE  AND  THICKNESS  OF  SLABS. — Slabs  shall  not  contain  more  than  36 
square  feet  or  have  any  dimension  greater  than  6  feet.  For  greater  area, 
slabs  shall  be  reinforced  with  i-inch  rods,  not  more  than  9  inches  apart, 
or  other  reniforcement  equally  as  strong: 

The  minimum  thickness  of  the  pavement  shall  not  be  less  than  4  inches. 

SUB-BASE. — The  sub-base  shall  be  thoroughly  rammed,  and  all  soft 
spots  removed  and  replaced  by  some  suitable  hard  material. 

When  a  fill  exceeding  one  foot  in  thickness  is  required,  it  shall  be 
thoroughly  compacted  by  flooding  and  tamping  in  layers  of  not  exceeding 
6  inches  in  thickness,  and  shall  have  a  slope  of  not  less  than  1  to  H. 

The  top  of  all  fills  shall  extend  at  least  12  inches  beyond  the  side- 
walk. 

While  compacting,  the  sub-base  shall  be  thoroughly  wetted  and  shall 
be  maintained  in  that  condition  until  the  concrete  is  deposited. 

BASE. — The  concrete  for  the  base  shall  be  so  proportioned  that  the 
cement  shall  overfill  the  voids  in  the  fine  aggregate  by  at  least  5  per  cent, 
and  the  mortar  shall  overfill  the  voids  in  the  coarse  aggregate  by  at  least 
10  per  cent.  The  proportions  shall  not  exceed  one  part  of  cement  to 
eight  parts  of  the  fine  and  coarse  aggregates.  WThen  the  voids  are  not 
determined  the  concrete  shall  have  the  proportions  of  one  part  cement, 
three  parts  fine  aggregates  and  five  parts  coarse  aggregates.  A  sack  of 
cement  (90  Ibs.)  shall  be  considered  to  have  a  volume  of  one  cubic 
foot, 

MIXING. — The  ingredients  of  concrete  shall  be  thoroughly  mixed  to 
the  desired  consistency,  and  the  mixing  shall  continue  until  the  cement 
is  uniformly  distributed,  and  the  mass  is  uniform  in  color  and  homo- 
geneous. 

a.  Measuring  Proportions.     Methods  of  measurement  of  the  proportions 
of  the  various  ingredients  including  the  water,  shall  be  used  which  will 
secure  separate  uniform  measurements  at  all  times. 

b.  Machine    Mixing.     Wlien    the    conditions    will    permit,    a    machine 
mixer  of  a  type  which  insures  the  proper  mixing  of  the  materials  through- 
out the  mass  shall  be  used. 

c.  Hand  Mixing.     When  it  is  necessary  to  mix  by  hand,  the  mixing 
shall  be  on  a  water-tight  platform  and  especial  precautions  shall  be  taken 
to  turn  the  materials  until  they  are  homogeneous  in  appearance  and 
color. 

d.  Consistency.     The  materials  shall  be  mixed  wet  enough  to  produce 
a  concrete  of  such  a  consistency  as  will  flush  readily  under  light  tamping, 
and  which,  on  the  other  hand,  can  be  conveyed  from  the  mixer  to  the 
forms  without  separation  of  the  coarse  aggregate  from  the  mortar. 

e.  Retempering.     Retempering  mortar  or  concrete,  i.  e.,  remixing  with 
water  after  it  has  partially  set,  shall  not  be  permitted. 

PLACING  OF  CONCRETE. — a.  Methods.  Concrete  after  the  addition  of 
water  to  the  mix  shall  be  handled  rapidly  to  the  place  of  final  deposit, 
and  under  no  circumstances  shall  concrete  be  used  that  has  partially 
set. 

6.  Freezing  weather.  The  concrete  shall  not  be  mixed  or  deposited 
at  a  freezing  temperature  unless  special  precautions  are  taken  to  avoid 
the  use  of  materials  containing  frost  or  covered  with  ice  crystals,  and  in 
providing  means  to  prevent  the  concrete  from  freezing  after  being  placed 
in  position  and  until  it  has  thoroughly  hardened. 

Sidewalks  shall  be  laid  in  such  a  manner  as  to  insure  the  protection  of 
the  pavement  from  injury  due  to  changes  in  foundations  or  from  con- 
traction and  expansion. 


SIDEWALKS,  CURBS  AND  GUTTERS  443 

Workmen  shall  not  be  permitted  to  walk  on  freshly  laid  concrete, 
and  where  sand  or  dust  collects  on  the  base  it  shall  be  carefully  removed 
before  the  wearing  surface  is  applied. 

WEARING  SURFACE. — The  wearing  course  shall  have  a  thickness  of  at 
least  1  inch. 

The  wearing  surface  shall  be  mixed  in  the  same  manner  as  the  mortar 
for  the  base,  but  the  proportion  one  cement  to  two  of  fine  aggregate,  and 
it  shall  be  of  such  consistency  as  will  not  require  tamping,  but  will  be 
readily  floated  with  a  straight-edge. 

The  wearing  surface  shall  be  spread  on  the  base  immediately  after  mixing, 
and  in  no  case  shall  more  than  50  minutes  elapse  between  the  time  that  the 
concrete  for  the  base  is  mixed  and  the  time  that  the  wearing  course  is 
floated. 

After  being  worked  to  an  approximately  true  surface,  the  slab  markings 
shall  be  made  directly  over  the  joints  in  the  base  with  a  tool  which  shall 
cut  clear  through  to  the  base  and  completely  separate  the  wearing  courses 
of  adjacent  slabs. 

The  slabs  shall  be  rounded  on  all  surface  edges  to  a  radius  of  not  less 
than  £-inch. 

WThen  required  the  surface  shall  be  troweled  smooth. 

The  application  of  neat  cement  to  the  surface  in  order  to  hasten  the 
hardening  is  prohibited. 

On  grades  exceeding  5  per  cent,  the  surface  shall  be  roughened.  This 
may  be  done  by  the  use  of  a  grooving  tool,  toothed  roller,  brush,  wooden 
float  or  other  suitable  tool;  or  by  working  coarse  sand  or  screenings  into 
the  surface. 

Where  color  is  used  it  shall  be  incorporated  uniformly  and  the  quantity 
and  quality  shall  be  such  as  to  not  impair  the  strength  of  the  wearing 
surface. 

SINGLE-COAT  WORK. — Single-coat  work  shall  be  composed  of  one  part 
of  cement,  two  parts  of  fine  aggregate  and  three  parts  of  coarse  aggregate, 
and  the  slabs  separated  as  provided  for  in  the  specifications  for  two-coat 
work. 

The  concrete  shall  be  firmly  compacted  by  tamping  and  evenly 
struck  off  and  smoothed  to  the  top  of  the  form.  Then  with  a  suitable 
tool  the  coarser  particles  of  the  concrete  shall  be  tamped  to  a  depth  which 
will  permit  of  finishing  the  walk  as  under  "  Wearing  Surface." 

PROTECTION  AND  GRADING. — When  completed,  the  walk  shall  be  kept 
moist  and  protected  from  traffic  and  the  elements  for  at  least  three 
days. 

Grading  after  the  walks  are  ready  for  use  should  be  on  the  curb  side  of 
the  sidewalk,  1£  inches  lower  than  the  sidewalk,  and  not  less  than  ^-inch 
to  the  foot  fall  towards  the  curb  or  gutter.  On  the  property  side  of  the  walk 
the  ground  should  be  graded  back  at  least  2  feet  and  not  lower  than 
the  walk;  this  will  insure  the  frost  throwing  the  walk  alike  on  both 
sides. 

CURBS. — The  trench  shall  be  excavated  to  a  depth  not  greater  than 
the  bottom  of  the  curb  and  a  width  not  greater  than  the  thickness  of  the 
curb  plus  6  inches. 

The  thickness  of  the  curb  shall  not  be  less  than  6  inches. 

After  the  forms  are  set  about  1  inch  of  wearing  surface  shall  be  placed 
on  the  inside  of  the  curb  form,  then  the  concrete  shall  be  deposited  at 
one  operation  and  firmly  tamped  to  within  1  inch  of  the  top  of  forms. 
The  top  wearing  surface  shall  then  be  placed  and  be  of  the  same  composi- 
tion as  that  specified  for  sidewalks. 

Joints  shall  be  made  three-fourths  the  depth  of  the  curb,  continuous 
with  joints  of  the  sidewalk  and  in  no  case  more  than  6  inches  apart. 


444  THE  ART  OF  ROADMAKING 

The  forms  shall  be  removed  as  soon  as  practicable  and  the  faces  finished 
at  one  operation,  floating  down  6  inches  with  a  one  to  one  mixture  of 
cement  and  fine  aggregate  of  sufficient  thickness  to  produce  a  smooth 
surface. 

Where  a  combination  curb  and  gutter  is  required,  they  shall  be  cast 
at  the  same  time  and  finished  at  one  operation. 


CURBS  AND  GUTTERS 

Curbstones  are  employed  for  the  outer  side  of  the  foot- 
ways to  sustain  the  coverings  and  form  the  gutter. 
Their  upper  edges  are  set  flush  with  the  sidewalk, 
so  that  the  water  can  flow  over  them  into  the  gutters. 

The  disturbing  forces  which  the  curb  has  to  resist  are:  (1) 
the  pressure  of  the  earth  behind  it,  which  is  frequently  aug- 
mented by  piles  of  merchandise,  building  materials,  etc., 
tending  to  overturn  it,  break  it  transversely,  or  move  it  bodily 
on  its  base;  (2)  the  pressure  due  to  the  expansion  of  freezing 
earth  behind  and  beneath  it,  especially  where  the  sidewalk 
is  partly  sodded  and  the  ground  is  accordingly  moist,  tending 
to  thrust  the  curb  forward;  (3)  the  concussions  and  abrasions 
caused  by  the  traffic,  the  defacement  and  injury  to  the  curb 
from  fires  built  in  the  gutters,  and  the  breaking,  displacing 
and  destruction  resulting  from  posts  and  trees  set  too  near 
the  curb. 

The  use  of  drain-tiles  under  the  curb  is  a  subject  of  much 
difference  of  opinion  among  engineers.  Where  the  subsoil 
contains  water  naturally,  or  is  likely  to  receive  it  from  outside 
the  curblines,  the  use  of  drains  is  of  decided  benefit,  but 
great  care  must  be  exercised  in  jointing  the  drain-tiles  lest  the 
soil  shall  be  loosened  and  removed  and  cause  the  curb  to 
drop  out  of  alignment. 

The  materials  employed  for  curbing  are  the  natural  stones, 
as  granite,  sandstone,  etc.,  artificial  stone,  fire-clay,  and  cast 
iron. 

The  dimensions  of  curbstones  vary  considerably  in  different 
localities,  and  according  to  the  width  of  the  footpaths:  the 
wider  the  path  the  wider  should  be  the  curb.  It  should, 
however,  never  be  less  than  8  inches  deep,  nor  narrower  than 
4  inches.  Depth  is  necessary  to  prevent  the  curb  turning  over 


SIDEWALKS,  CURBS   AND  GUTTERS 


445 


towards  the  gutter.  It  should  never  be  in  less  lengths  than 
3  feet.  The  top  surface  should  be  beveled  off  to  conform  to 
the  slope  of  the  footpath  and  the  front  face  should  be  hammer- 
dressed  for  a  depth  of  about  6  inches,  in  order  that  there  may 
be  a  smooth  surface  visible  against  the  gutter.  The  back  for 
3  inches  from  the  top  should  be  also  dressed,  so  that  the 
flagging  or  other  paving  may  butt  fair  against  it.  The  end- 


FIG.  239. — View  Showing  Expansion  of  Concrete  Sidewalk,  Chicago. 

joints  should  be  cut  truly  square,  the  full  thickness  of  the 
stone  at  the  top,  and  so  much  below  the  top  as  will  be 
exposed;  the  remaining  portion  of  the  depth  and  bottom 
should  be  roughly  squared,  and  the  bottom  should  be  fairly 
parallel  to  the  top. 

Setting  curb  requires  care  and  an  experienced  workman, 


446 


THE   ART   OF  ROADMAKING 


for  as  it  is  set  dry,  great  care  must  be  exercised  to  set  it  true 
to  level  and  line.     It  must  be  well  rammed  and 

letting          bedded  or  it  will  sink,  turn  slightly  over  or  move, 
even   months   after   it   has   been   set.     Curbstones 

carelessly  set  will  never  present  a  pleasing  appearance. 

Curbstones  to  be  set  in  concrete  should   be  first  set  and 

blocked  in  position  on  grade  and  line.     The  blocking  should 


K --- 24" — H 

FIG.  240.— Vitrified  Clay  Block  for  Street  and  Road  Curbing. 
(See  also  Fig.  188,  Chap.  XV.) 


FIG.  241. — Concrete  Curb  and  Gutter. 

be  done  with  brick,  paving-stones,  or  other  imperishable 
material. 

For  tamping  the  concrete  under  and  around  curbstones,  a 
wooden  tamper  made  of  a  piece  of  seasoned  oak  2  inches 
by  4  inches,  about  5  feet  long,  shod  with  ^-inch  iron,  forms 
an  excellent  tool. 

The  concreting  of  the  curbs  (which  should  be  done  in  advance 
of  the  roadway  concreting)  is  best  performed  by  first  filling 


SIDEWALKS,  CURBS  AND  GUTTERS 


447 


underneath  from  the  roadway  side,  then  upon  the  face  and 
back  up  to  the  grade  of  the  roadway;  then  filling  up  behind 
the  stones  to  the  required  height,  removing  all  blocking  as 
the  concrete  is  tamped  in,  taking  care  not  to  disturb  the 
alignment  of  the  curb  and  to  see  that  every  space  is  filled  solid 
with  the  concrete. 

In  setting  curbstones  the  ends  should  be  kept  from  actual 
contact,  by  strips  of  ^-inch  iron  temporarily  inserted  as  they 
are  set  and,  after  the  roadway  concrete  is  laid,  the  joints 
should  be  filled  with  a  thin  grout  composed  of  equal  parts  of 
Portland  cement  and  sand.  This  should  be  done  by  first 


K --Z4" 

FIG.  242. — Concrete  Curb  and  Gutter. 

pressing  a  small  amount  of  stiff  mortar  into  the  joints  at  the 
face  and  bark  and  then  pouring  the  grout  in  from  the  top 
until  the  joint  is  full.  If  these  joints  are  not  filled  solid,  but 
simply  smeared  over  the  surface  with  a  little  mortar  which 
penetrates  but  a  half-inch  or  less,  it  will  only  be  a  question 
of  a  short  time  when  it  will  drop  off  and  leave  a  cavity  between 
the  stones. 

In  localities  where  stone  is  not  obtainable,  artificial  stone, 
fire-clay  curb,  and  cast  iron  afford  excellent  substitutes. 
Fire-clay  curbing  is  extensively  used  with  brick  pavements. 

Cast  iron  cast  in  L-shaped  sections  is  employed  in  some 
cities  in  France. 

In  streets  covered  with  broken  stone,   a  stone  gutter  is 


448  THE  ART  OF  ROADMAKING 

necessary.     It  may  be  formed  of  either  stone  slabs  or  paving- 
blocks,  the  latter  being  the  better,  and  it  should 
be  not  less  than  18  inches  wide.     If  formed  of  paving- 
blocks,  the  blocks  should  be  laid  with  their  length  parallel 
to*the  curb,  bedded  on  gravel,  and  well  grouted  in  with  bitu- 
minous cement. 

When  stone  slabs  are  used,  they  should  be  not  less  than 
3  feet  long,  6  inches  thick,  and  from  10  to  15  inches  in  width. 
They  should  be  laid  so  that  they  will  not  be  of  uniform  width, 


FIG.  243. — Type  of  Concrete  Curb  with  Slanting  Outer  Face.     Used  in 

Country  Work. 

otherwise  the  continuous  longitudinal  joint  between  the  gutter 
and  the  rest  of  the  pavement  will  quickly  wear  into  long  deep 
ruts  or'  grooves,  causing  severe  strains  upon  the  running-gear 
of  vehicles  when  attempting  to  leave  it. 

The  gutter  should  have  the  same  slope  as  the  roadway,  and 
the  curb  should  show  7  inches  or  more  above  it. 

In  streets  paved  with  asphalt,  granite  blocks,  or  bricks  the 
same  material  is  used  for  the  gutters;  the  blocks  being  laid 
with  their  length  parallel  to  the  curb,  instead  of  transversely 
as  in  the  street  itself. 

Street-crossings  are  formed  of  two  or  more  rows  of  stone 


SIDEWALKS,  CURBS  AND  GUTTERS  449 

slabs,  usually  with  one  or  more  rows  of  paving-blocks  between 
them.  The  stone  used  should  not  be  less  than 
3  feet  long,  10  inches  wide,  and  6  inches  thick,  with 
the  top  surface  hammer-dressed,  the  ends  cut  to 
a  bevel  of  about  15  degrees,  arid  dressed  so  as  to  form  a  close 
joint  for  the  full  depth  of  the  stone.  The  reason  for  beveling 
the  joints  is  to  cause  the  traffic  to  travel  across  the  joint 
instead  of  along  it,  and  thus  prevent  the  formation  of  the 
ruts  which  happens  with  right-angled  joints.  The  beveled 
joints  must  point  towards  the  center  of  the  intersection, 
otherwise  the  desired  result  will  not  be  obtained,  and  ruts 
will  be  formed. 


CHAPTER   XXI 
MISCELLANEOUS  ROADS   AND  PAVEMENTS 

STONE  trackways  were  used  in  ancient  Egypt  for  lowering 
the  tractive  resistance  in  moving  great  weights,  and  in 
modern  times  they  have  been  used  in  nearly  every  European 

country  and  in  America.  (See  p.  8.)  Their  use 
fr°nkw  on  an  extensive  scale  has,  however,  been  abandoned 

except  in  Northern  Italy.  Those  in  use  in  Italy 
consist  of  two  parallel  lines  of  granite  blocks,  14  inches  wide 
by  8  inches  deep  by  5  feet  long,  bedded  in  a  layer  of  sand. 
The  lines  are  28  inches  apart,  with  a  footway  for  horses  be- 


tween,  paved  with  cobbles.  This  footway  has  a  slight  inclina- 
tion downwards  towards  the  center,  thus  serving  as  a  channel 
to  receive  the  surface  water,  which  finally  escapes  into  the 
sewers  through  stone  gratings. 

The  steel  trackways  that  have  been  constructed  consist  of 
two  parallel  lines  of  steel  plates,  8  inches  wide,  laid  at  a  suffi- 
cient distance  apart  to  receive  the  wheels  of  vehicles 
trackwa  s     °^  ^e  standard  gauge.     The  plates  are  provided  on 
one  edge  with  a  flange  ^  inch  wide,   and  on   the 
under  side  with  a  flange  about  6  inches  deep,  which,  when 
bedded  in  the  earth  of  the  roadway,  supports  the  rail  without 
the  use  of  cross-ties.     Tie-rods  are  used  at  intervals  of  about 
10  feet. 

450 


MISCELLANEOUS  ROADS  AND  PAVEMENTS  451 

The  advantages  claimed  for  the  steel-track  wagon  road  are: 
(1)  that  it  can  be  built  without  greater  cost  in  most  cases, 
and  probably  with  less  cost  in  many  cases,  than  any  other 
hard  and  durable  road;  (2)  that  it  will  last  many  times  as 
long  as  any  other  known  material  for  road  purposes  and  with 
much  less  repair;  (3)  that  the  power  required  to  move  a 


FIG.  245.— The  Steel  Track  as  a  Bicycle  Path. 

vehicle  over  the  steel-track  road  is  only  a  small  fraction  of 
the  power  required  to  move  the  same  vehicle  over  any  other 
kind  of  road. 

During  1892  a  steel  trackway  was  constructed  between 
Valencia  and  Grao,  Spain,  to  replace  a  stone  road  which  cost 
$5470  a  year  to  maintain.  It  is  traversed  daily  by  an  average 
of  3200  vehicles,  each  of  which  pays  a  toll  of  about  eight- 
tenths  of  a  cent,  and  the  annual  cost  of  maintenance  is  about 


452  THE  ART  OF  ROADMAKING 

$380,  but  for  various  local  reasons  this  cannot  be  taken  as  a 
guide  for  American  practice. 

In  regard  to  durability,  the  claim  is  true-  only  as  far  as  the 
steel  rails  are  concerned,  as  the  surface  adjoining  the  rails, 
whatever  it  may  be,  will  in  a  comparatively  short  time,  be 
worn  into  ruts  by  vehicles  turning  on  and  off  the  steel 
rails. 

The  most  serious  disadvantages  of  the  steel  trackway  is 
that  if  it  does  not  have  a  permanent  footway  for  the  horses, 
it  is  least  effective  in  a  muddy  time,  when  it  is  most  needed; 
and  if  it  does  have  a  permanently  hard  surface  between 
the  rails,  the  cost  is  unreasonable.  If  a  steel  trackway  is  laid 
in  a  broken-stone  road,  the  additional  cost  will  be  (1)  the  cost 
of  the  metal,  (2)  the  cost  of  placing  the  metal,  including  the 
increased  cost  of  compacting  the  broken  stone,  and  (3)  the 
increased  cost  of  maintenance. 

Another  objection  is  that  owing  to  the  narrow  space  between 
the  rails,  the  horses  are  compelled  frequently  to  step  upon 
the  rails,  the  smooth  surfaces  of  which  interfere  with  their 
footing,  which  in  a  measure  neutralizes  the  advantages  of  a 
smooth  track  for  the  wheels.  Still  another  objection  is  that 
the  gauge  of  vehicles  varies  considerably,  and  consequently 
either  the  face  of  the  rail  must  be  very  wide,  which  increases 
the  expense,  or  some  vehicles  cannot  be  accommodated.  The 
conclusion  is,  therefore,  that  trackways  are  out  of  date,  that 
they  are  more  expensive  and  less  effective  than  good  macadam 
roads,  and  that  for  a  country  where  an  ordinary  macadam 
road  does  not  suffice,  a  first-class  pavement  or  a  railroad 
should  be  built. 

Concrete  blocks  have  frequently  been  experimented  with  in 
connection  with  trackways,  but  their  uses  for  horse-propelled 
vehicles  are  subject  to  the  same,  or  even  more  serious, 
Concrete-  disadvantages,  as  the  stone  and  steel  trackways, 
trackways  Their  use  has,  however,  been  successful  in  con- 
nection with  automobile  traffic,  by  decreasing  not 
only  the  resistance,  but  also  the  wear  on  the  road  and  the 
cost  of  maintenance. 

Fig.  246  shows  a  section  of  a  concrete-block  trackway  built 


MISCELLANEOUS  ROADS  AND   PAVEMENTS  453 


FIG.  246.— Concrete-block  Trackway,  Orlando,  Fla. 


FIG.  247. — Reversible  Concrete  Block. 


454 


THE  ART  OF  ROADMAKING 


FIG.  248. — Road  Making  as  a  Fine  Art. 

Laborers  engaged  in  building  a  special  motor-car  road  in  Paris,  each  individual 
bit  of  stone  being  carefully  placed  by  hand. 


MISCELLANEOUS  ROADS  AND  PAVEMENTS  455 

near  Orlando,  Florida,  which,  in  two  years  of  continual  use, 
required  no  repairs. 

The  block  is  12  inches  wide,  8  inches  thick,  and  24  inches 
long,  with  a  groove  1J-  inches  deep  and  6  inches  wide  at  the 
bottom,  curving  in  a  convex  form  to  the  flange  on  the  outside, 
the  flange  showing  a  surface  of  2  inches.  When  laid,  the 
surface  of  the  flange  should  be  flush  with  the  surrounding 
soil.  The  blocks  are  held  together  with  a  tongue  and  groove 
arrangement  that  keeps  the  ends  from  working  up  or  down, 
and  the  flange  on  the  bottom  of  the  block  keeps  it  from  having 
any  side  motion,  every  block  being  thus  held  rigidly  in  position. 
The  blocks  are  reversible,  so  that  when  one  side  shows  any 
effect  of  wear,  it  can  be  turned  over  and  the  road  given  a 
new  surface. 

It  is  claimed  that  heavily  loaded  wagons  can  be  turned  out  of 
this  track  road  with  little  difficulty,  without  the  road  suffering 
from  such  wear.  The  block  are  made  of  carefully  mixed  and 
tamped  concrete  and  can  be  made  along  the  road  on  which 
they  are  to  be  used,  and  if  sand  and  gravel  of  good  character 
are  near  the  highway,  the  road  can  be  resurfaced  at  very 
low  cost. 

Artificial  granite  blocks  are  formed  from  the  chippings  of 
granite   quarries,   mixed  with   Portland   cement   in  sufficient 
quantity  to  make  a  thorough  bond  between  the 
pieces.     It  is  put  down  in  blocks  or  squares,  and       Artificial 
the   surface   is   kept   comparatively   rough  by  the       bloci 
cement  wearing  below  the  points  of  the  granite. 
Its  only  advantage  is  cheapness. 

In  localities  where  timber  is  abundant  and  other  materials 
are  unobtainable,  planks  may  be  employed  to  form  pave- 
ments. The  first  plank  road  on  the  continent  was 
built  in  Canada  in  1836;  they  then  became  some- 
what  common  in  the  heavily  timbered  portion  of 
the  northern  United  States  and  of  Canada,  and  were  very 
advantageous  in  the  building  up  of  new  districts,  but  very 
few  of  them  are  now  in  existence. 

When  new  and  when  kept  in  repair,  plank  roads  make  a 
comparatively  smooth  roadway  possessing  some  advantages 


456  THE  ART  OF  ROADMAKING 

for  both  light  and  heavy  traffic.  The  planks  are,  however, 
very  likely  to  be  displaced,  even  when  spiked  down,  and  are 
likely  to  be  floated  away,  when  not  spiked  down,  and  when 
in  this  condition  they  make  a  very  disagreeable  road.  Main- 
tenance is  expensive,  as  being  alternately  wet  and  dry,  the 
plank  rots  rapidly  and  at  best  does  not  last  more  than  five 
years,  and  often  only  two. 

In  construction,  plank  roads  are  usually  about  8  feet  wide, 
and  occupy  one  side  of  an  ordinary  earth  road,  the  other 
side  being  used  to  turn  out  upon  and  for  travel  during  the  dry 
season.  The  method  of  construction  most  commonly  followed 
is  to  lay  the  boards  perpendicular  to  the  axis  of  the  road,  as 
this  position  is  more  favorable  to  their  wear  and  tear  than 
any  other,  besides  being  the  most  economical. 

Their  ends  are  not  in  an  unbroken  line,  but  so  arranged 
that  the  ends  of  every  three  or  four  project  alternately,  on 
each  side  of  the  axis  of  the  road,  3  or  4  inches  beyond  those 
next  to  them.  This  presents  a  short  shoulder  to  the  wheels 
of  vehicles  to  facilitate  their  coming  upon  the  plank  surface 
when  they  may  have  turned  aside  and  prevents  the  formation 
of  long  ruts  at  the  edges  of  the  road.  Often  the  boards  have 
been  spiked  to  the  sills,  but  this  is  unnecessary,  the  stability 
of  the  boards  being  best  secured  by  well  packing  the  earth 
between  and  around  the  sills,  so  as  to  present  a  uniform 
bearing  surface  to  the  boards,  and  by  adopting  the  usual 
precautions  for  keeping  the  subsoil  well  drained  and  preventing 
any  accumulation  of  rain-water  on  the  surface.  The  boards 
were  often  covered  with  gravel,  sand,  or  loam  to  protect  them 
from  wear. 

Corduroy,  or  log,  roads  are  make-shifts  employed  in  tim- 
bered districts  to  carry  a  road  over  soft,  swampy  ground 
always  kept  moist  by  springs  and  which  cannot  be  drained 
without  too  much  expense.  They  are  built  by  felling  a 
sufficient  number  of  young  trees,  as  straight  and  as  uniform 
as  possible,  and  laying  them  side  by  side  across 

the  road  at  right  an&les  to  its  length.     Though  its 
successive  hills    and  hollows    offer  great  resistance 
to  draught  and  are  very  unpleasant  to  persons  riding  over 


MISCELLANEOUS  ROADS  AND  PAVEMENTS  457 

it,  it  is  nevertheless  a  very  valuable  substitute  for  a  swamp, 
which  in  its  natural  state  would  at  times  be  utterly  impassable, 
and  with  sufficient  care  such  roads  may  be  made  fairly  smooth 
when  new,  but  they  grow  exceedingly  rough  with  age. 

In  some  of  the  Western  States,  where  wood  is  abundant 
and  cheap,  and  gravel  scarce,  roads  for  light  traffic  have 
been  made  by  felling  and  burning  the  timber,  and 
covering  the  road  with  the  charcoal.  Poles  from 
6  to  16  inches  in  diameter  are  cut  and  piled  lengthwise  along 
the  road  about  6  feet  high,  being  9  feet  on  the  bottom  and 
2  on  top,  and  then  covered  with  straw  and  earth,  or  simply 
with  sods,  and  burned  in  the  manner  of  coal-pits.  The 
covering  is  taken  from  the  sides  of  the  road,  and  the  ditches 
thus  formed  afford  good  drainage.  After  the  timber  is  con- 
verted into  charcoal,  the  earth  is  removed  to  the  side  of  the 
ditches,  the  coal  raked  down  to  a  width  of  15  feet,  leaving 
it  2  feet  thick  at  the  center  and  1  foot  at  the  sides,  and  the 
road  is  completed.  The  charcoal,  being  soft  and  friable,  should 
be  covered  with  a  thin  layer  of  earth  or  gravel  for  greater 
durability,  and  to  prevent  it  from  blowing  or  washing 
away. 

Slag  and  cinders  from  iron  and  copper  works  may  be  em- 
ployed with  advantage  when  they  are  procurable,  and  when 
no  stone  sufficiently  tough  to  withstand  the  action 
of  heavy  traffic  can  be  obtained.     The  slag  from 
modern  steel  furnaces  is  comparatively  light,  has   a  sponge- 
like  structure,  and  contains  a  large  amount  of  lime.     When 
used  for  roads  this  variety  compacts  very  readily  and  forms 
an   even   and   hard   surface.     Steel-furnace    slag   dust   has   a 
high  cementing  power. 

Coal-slack  is  sometimes  used  for  road  building  where  neither 
stone  nor  gravel  is  obtainable  at  reasonable  cost.  The  slack 
is  friable  and  easily  grinds  to  powder,  but  makes 
a  fair  road  for  light  traffic.  In  many  localities, 
where  there  are  quantities  of  slack,  it  could  be 
profitably  spread  upon  the  roads,  and  being  light,  the  haulage 
is  easy. 

The    clinkers   produced   by   burning   street   sweepings   and 


458 


THE  ART  OF  ROADMAKING 


s 


MISCELLANEOUS  ROADS  AND  PAVEMENTS  459 

garbage  and  the  debris  produced  in  the  manufacture  of  gas, 
consisting  of  the  clinkers,  old  retorts,  fire-bricks, 
ash-pan  and  coke  refuse,  have  all  been  tried  for 
paving  both  footpaths  and  carriageways,  with  some  satisfac- 
tion in  the  former,  but  in  the  latter  with  failure.  The  ma- 
terials are  prepared  by  crushing  to  a  size  of  about  one  inch; 
the  crushed  material  is  then  screened,  and  the  portion  that 
will  not  pass  through  a  J-inch  screen  is  used  for  the  top 
finish,  and  the  coarser  portion  for  the  foundation.  The 
materials  so  separated  are  mixed  with  either  Portland  cement 
or  coal-tar,  and  laid  in  place  in  the  usual  manner,  or  they 
may  be  formed  into  blocks  at  a  factory  and  shipped  to  the 
place  of  use. 

In  several  cities  where  crematories  are  employed  for  the 
destruction  of  the  garbage,  etc.,  the  clinker  therefrom  io 
used  for  making  concrete  slabs.  The  clinker  is 

ground  very  fine,  and  mixed  with  Portland  cement.       es  ruAc  or 

.  .  concrete. 

The    mass   of  clinker  and   cement  is  then   passed 

through  a  hydraulic  press  and  formed  into  slabs  2  inches  in 
thickness,  and  are  used  for  footpath  paving  under  the  name 
of  "Destructor"  concrete. 

Around  the  Chesapeake  Bay  and  the  Gulf  of  Mexico,  oyster 
shells  have  been  used  to  a  considerable  extent  to  make  roads 
for  light  traffic.     They  are  spread  loosely  over  the 
road  and  speedily  become  consolidated  by  the  traffic. 
The  shells  have  a  high  cementing  power  but  a  very 
low  resistance  to  crushing,  and  while  they  make  a  smooth 
road  surface,  it  is  soon  ground  to  powder,  producing  a  dis- 
agreeable dust,  and  requiring  the  constant  application  of  new 
shells  to  keep  it  from  rutting. 

Pavements  made  from  granulated  cork  mixed  with  asphalt 
and  other  cohesive  substances  have  been  employed  in  London 
and  other  European  cities  to  deaden  the  noise  in 
the  neighborhood  of  hospitals  and  churches.     The 
ingredients  are  compressed  into  blocks  measuring  9X4JX2 
inches,  which  are  imbedded  in  tar  and  rest  upon  a  concrete 
foundation  6  inches  thick. 

It  is  claimed  that  as  a  paving  material  it  is  non-absorbent. 


460  THE  ART  OF  ROADMAKING 

non-slippery,  practically  noiseless,  more  durable  than  wood, 
perfectly  sanitary,  and  not  subject  to  expansion  and  con- 
traction. Blocks  which  have  been  under  traffic  for  a  number 
of  years  have  given  very  satisfactory  results. 

Paving-bricks  are  made  in  Germany  from  copper  slag.     The 

slag  is  run  into  heated   cast-iron  moulds  having  a  capacity 

of  thirty-six  bricks;    immediately  after  filling,  the 

Copper  moulds  and  their  contents  are  thickly  covered  with 
slag. 

sand  and  allowed  to  stand  undisturbed  for  seventy- 
two  hours.  When  thoroughly  cooled  each  brick  is  struck 
a  strong  blow  with  a  hammer,  and  those  containing  blow- 
holes crack. 

Vulcanized  india  rubber  in  large  sheets  of  about  one  inch  in 
thickness  has  been  used  in  some  European  cities,  with  excellent 

satisfation.     It   is   laid   on   a   concrete   foundation, 

finished  to  a  smooth  bed,  on  which  the  sheets  of 
rubber. 

rubber  are  laid  and  held  in  place  by  strips  of  iron. 

It  has  met  nearly  all  the  requirements  of  a  perfect  paving 
material,  being  exceedingly  durable,  not  slippery,  absolutely 
noiseless  and  impervious,  but  its  cost  prohibits  its  more 
general  use. 

Rubber  has  been  used  in  London  on  two  roadways  passing 
under  the  hotel  of  the  Euston  terminal  station  of  the  London 
<fe  Northwestern  Ry.  This  was  laid  in  1881  at  a  cost  of  $5.60 
per  square  yard  for  concrete  foundation  and  $27.10  per  square 
yard  for  the  rubber  paving,  2  inches  thick.  In  1902  the  thick- 
ness had  been  reduced  by  wear  to  f-inch  in  some  places  and 
1  to  1^  inches  at  others.  Bids  for  new  rubber  paving  in  that 
year  were  from  $27.00  to  $86.22  per  square  yard. 

Artificial  paving  stones  are  manufactured  in  Germany  from 
a  mixture  of  coal-tar,  sulphur,  chlorate  of  lime,  glass,  or 
furnace  slag,  by  mixing  the  tar  and  sulphur  at 
Artificial  a  moderate  temperature  and  adding  the  chlorate  of 
stonef  lime.  This  mixture  is  allowed  to  cool,  then  is  broken 
into  small  fragments  and  mixed  with  fragments  of 
glass  or  blast-furnace  slag.  It  is  then  heated  to  a  moderate 
temperature,  placed  in  moulds  of  the  desired  form,  and  sub- 
jected to  a  pressure  of  about  3000  pounds  per  square  inch. 


MISCELLANEOUS  ROADS  AND  PAVEMENTS 


461 


The  advantages  claimed  for  this  material  are:  durability 
equal  to  that  of  many  stone  roads;  resistance  to  changes  of 
temperature;  a  roughness  of  surface  which  gives  horses  a 
good  foothold;  non-transmission  of  sound;  facility  of  clean- 
ing on  account  of  the  closeness  of  the  joints. 

A  roadway  for  heavy  automobile  traffic,  used  extensively 


FIG.  250. — Pavement  known  as  "Durax." 

in  England  and  Germany  is  called  "Durax/'  It  is  made 
of  3-inch  irregular  cubes  of  hard  stone,  laid  in  small 
segments  of  circles.  The  stones  are  cut  by  ma- 
chinery,  and  are  comparatively  inexpensive,  and 
are  laid  without  grout.  It  is  cheap,  almost  as  smooth  as 
macadam,  comparatively  noiseless,  affords  an  excellent  foot- 
hold for  horses,  and  is  very  durable. 


462 


THE  ART  OF  ROADMAKING 


CHAPTER   XXII 
THE   ROADSIDE 

No  matter  how  smooth  and  well  constructed  the  travelled 
way  may  be,  if  the  roadsides  are  not  cared  for,  the  road,  as 
a  whole,  will  not  give  a  good  impression.  All  rubbish  should 
be  removed  and  the  excavations  and  embankments  smoothed 
and  planted  with  grass  wherever  it  will  grow.  (See  Fig.  22.) 
Unsightly  brush  should  be  cut  and  grubbed  out.  Sometimes, 
however,  the  brush  and  the  small  trees,  if  suitably  trimmed, 
add  to  the  attractiveness  of  the  roadside. 

Air  and  sunshine  are  necessary  for  the  preservation  of  roads 
in  good  order;  water  and  want  of  light  are  among  the  most 
destructive  agents  in  nature,  and  no  road  can  be 


kept  in  order  which  is  always  in  ,  a  damp  state  and  a 


on  which  the  sun  never  shines.     Everything,  'there- 

fore that  prevents  a  perfect  circulation  and  distribution  of  the 

air  and  obstructs  the  revivifying  effects  of  sunshine  is  to  be 

avoided. 

Considered  from  a  purely  engineering  point  of  view,  there 
is  no  doubt  that  a  road  would  be  all  the  better  without  hedges 
and  fences  of  any  kind,  but  inasmuch  as  a  barrier  of  some 
kind  or  other  between  roads  and  the  adjoining  fields  is 
absolutely  necessary  on  other  grounds,  e.g.,  to  keep  cattle 
from  straying  from  one  to  the  other,  to  mark  the  limits  of 
property,  etc.,  a  hedge  may  be  considered  a  necessary  evil, 
and  the  point  for  the  consideration  of  the  engineer  is  how  to 
minimize  the  evil.  The  higher  and  thicker  the  hedge  the 
more  obstruction  must  it  offer  to  the  sun  and  wind.  The 
object  to  be  borne  in  mind  should  be  to  erect  such  a  barrier 
that  (1)  shall  allow  the  greatest  amount  of  light  and  air  to 
pass  through  it,  and  (2)  shall  best  answer  the  non-engineering 
purposes  for  which  it  is  required. 

463 


464 


THE  ART  OF  ROADMAKING 


According   to 


FIG.  252.— Sketch 
of  a  young  sap- 
ling, often  taken 
from  the  woods 
to  save  expense. 
The  roots  ex- 
tend long  dis- 
tances in  search 
of  food,  and 
these  and  the 
branches  are 
lopped  off  as  in- 
dicated. 


these  principles  the  best  barrier  would  be 
one  of  iron,  or  of  iron  and 
wood  combined,  provided 
that  it  was  sufficiently  strong 
to  resist  being  broken  down 
by  cattle,  horses,  etc.  Iron 
wire  should  not  be  used,  as 
it  is  easily  bent  out  of  shape, 
and  cattle  and  horses  are 
very  apt  to  injure  themselves 
in  attempting  to  jump  over 
the  fence  or  to  force  them- 
selves through  it,  while 
barbed  wire  is  still  more  ob- 
jectionable. 

A  strong  iron  fence  forms, 
perhaps,  the  best  barrier, 
but  it  is  costly,  and  few 
authorities  would  be  prepared  to  go  to 
the  expense  of  putting  it  up,  especially  as 
it  deteriorates  with  time  and  entails  a 
constant  charge  for  maintenance  in  conse- 
quence of  the  corrosion  of  the  iron  and  the 
necessity  for  periodically  painting  it. 

Wood  is  not  a  suitable  material  for  a 
fence,  as  it  is  easily  destroyed  and  rots 
under  the  effects  of  the  atmosphere;  but,  if 
used,  it  should  be  oak  or  some  other  kind 
which  resists  rot  as  long  as  possible.  Most 
kinds  of  wood  are  perfectly  useless  for  the 

purpose. 

.^,  Me.  M..M...  The    commonest 

fence  in  England  is 
the  hedge,  and  its 
almost  universal  use 
is  perhaps  due  to  the 
fact  that  it  is  cheap 
and  requires  no  skilled 


THE  ROADSIDE  465 

labor  to  maintain,  but  a  good  hedge  cannot  be  established 
without  care  in  planting  and  constant  subsequent  watch- 
fulness. 

One  of  the  first  engineers  who  drew  attention  to  the  im- 
portance of  hedges  in  connection  with  roads  was  John  Walker, 
who  said: 

"  The  fences  on  each  side  form  a  very  material  and  important 
subject  with  regard  to  the  perfection  of  roads;  they  should  in 
no  instance  be  more  than  5  feet  in  height  above  the  center  of 
the  road,  and  all  trees  which  stand  within  20  yards  of  it 
ought  to  be  removed.  I  am  sure  that  20  per  cent  of  the 
expense  of  improving  and  repairing  roads  is  incurred  by  the 
improper  state  of  the  fences  and  trees  along  the  side  of  it, 
on  the  sunny  side  more  particularly.  This  must  be  evident 
to  any  person  who  will  notice  the  state  of  a  road  which  is 
much  shaded  by  high  fences  and  trees,  compared  to  the  other 
parts  of  the  road  which  are  exposed  to  the  sun  and  air.  My 
observations  with  regard  to  fences  and  trees  apply  when  the 
road  is  on  the  same  level  as  the  adjacent  field;  but  in  many 
cases  on  the  most  frequented  roads  in  England  more  stuff 
has  been  removed  from  time  to  time  than  was  put  on;  the 
surface  of  the  road  is  consequently  sunk  into  a  trough  or 
channel  from  3  to  6  feet  below  the  surface  of  the  fields  on 
each  side.  Here  all  attempts  at  drainage  or  even  common 
repairs  seem  to  be  quite  out  of  the  question;  and  by  much 
the  most  judicious  and  economical  mode  will  be  to  remove 
the  whole  road  into  the  field  which  is  on  the  sunny  side 
of  it." 

Mr.  Law,  in  his  work  on  "Roads/7  make  some  very  useful 
observations : 

"Few  persons  are  aware  of  the  extent  to  which  a  road 
may  be  injured  by  high  hedges  or  lines  of  trees.  Trees  are 
worse  than  hedges,  because  they  not  only  deprive  the  road 
of  the  action  of  the  air  and  sun,  but  they  further  injure  it 
by  the  dripping  of  rain  from  their  leaves,  as  a  consequence 
of  which  the  road  is  kept  in  a  wet  state  long  after  it  would 
otherwise  have  become  dry. 

"When  fences  are  indispensable  they  should  be  placed  as 
far  as  may  be  from  the  sides  of  the  road,  and  should  be  kept 
as  low  as  possible.  When  there  is  a  deep  ditch  on  either  side 
of  the  road  it  becomes  necessary,  to  prevent  accident,  that 
the  fence  should  be  placed  between  the  road  and  the  ditch, 


466 


THE  ART  OF  ROADMAKING 


FIG.  253.— Type  of  the 
"  Undesirable  .  Citi- 
zen." 

This  represents  two 
kinds  of  trees — often 
imposed  upon  innocent 
customers;  one  kind, 
an  overgrown  nursery 
tree,  passed  ovef  for 
some  defect  and  gen- 
erally sold  cheaply- 
after  being  "  pre- 
pared" as  shown.  It 
is  first  cut  back  so  that 
the  tall,  rambling  top 
may  not  overdraw  on 
the  impaired  vitality 
of  the  mangled  roots 
— which  have  been  cut 
off  near  the  trunk  to 
save  the  excavation 
and  cost  of  caring  for 
full  roots.  The  other 
kind  is  a  young  sap- 
ling taken  from  the 
woods  —  overgrown 
and  cut  back,  and  the 
roots  greatly  extended 
in  search  of  susten- 
ance, are  cut  off,  with 
the  effect  noted. 


THIS  TREE  CAN  NEVER  GROW  A 
NATURAL  CHARACTERISTIC  TOP, 
AND  WILL  DISCLOSE  MANY  DE- 
FECTS IN  DEVELOPMENT. 


but  in  other  situations  the  fence 
should  be  placed  on  the  field 
side  of  the  ditch.  In  so  doing 
the  surface  draining  of  the  road 
into  the  side  ditches  is  less 
interfered  with  and  the  action 
of  air  and  sunshine  is  less  ob- 
structed by  the  fence. 

"  The  different  descriptions  of 
fence  which  may  be  employed 
are  various.  In  districts  where 

/stone  is  plentiful,  and  especially 
in  the  immediate  neighborhood 
of  quarries,  where  stone  rubble 
can  be  obtained  at  a  trifling 
cost,  dry  rubble  walls,  without 
any  mortar,  are  very  good  and 
cheap  and  require  little  or  no 
repair. 

"  For  the  road  itself,  an  open 
post-and-rail  fence  is  the  best 
which  can  be  employed,  because 
it  scarcely  impedes  the  action  of 
the  wind  and  the  sun  upon  the 
surface  of  the  road,  but  the  great 
practical  objection  to  timber 
fences  is  their  liability  to  decay, 
which  occasions  frequent  and 
constant  expense  for  renewal. 

"The  most  common,  and,  all 
things  considered,  the  most  use- 
ful fence  is  the  quickset  hedge. 
If  properly  planted  and  care- 
fully attended  to  for 
the  first  few  years,  a 
natural  fence  may  be 
obtained  sufficiently 
strong  to  resist  the 
efforts  of  cattle  to 
break  through,  and 
very  economical  in  cost 
for  maintenance.  A 
bank  or  mound  of 
earth  at  least  2  feet 
in  depth  should  be 


THE  ROADSIDE  467 

prepared  for  the  reception  of  the  quicks,  which  should  be  three 
years'  plants  which  have  been  transplanted  two  years.  The 
best  kind  of  soil  is  one  of  a  light  sandy  nature  admitting 
sufficient  moisture  to  nourish  the  plants  and  retaining  moisture 
in  dry  seasons.  Heavy  clay  soils  are  not  sufficiently  pervious 
to  water,  and  plants  placed  in  such  soils  are  never  found  to 
thrive.  A  mixture  of  rotten  leaves  is  of  great  use  and  causes 
the  plants  to  grow  with  much  vigor.  The  quicks  are  most 
commonly  planted  in  a  single  row,  at  distances  of  about 
4  inches  apart.  But  a  much  better  hedge  is  formed  by  plant- 
ing them  6  inches  apart  in  a  double  row,  as  shown  below,  with 
a  space  of  6  inches  between  the  rows, 

O  O  O  O  0  O  0 

O  O  O  O  O  O 

and  so  arranged  that  the  plants  in  one  row  are  opposite  the 
spaces  in  the  other.  By  this  arrangement,  although  the 
plants  are  really  not  so  crowded,  and  have  more  space  around 
their  roots  from  which  to  derive  nourishment  than  in  a  single 
row,  they  form  a  thicker  hedge.  The  proper  time  for  planting 
quicks  is  during  the  autumn  or  the  spring,  and,  in  fine  seasons, 
the  operation  may  be  continued  during  the  whole  winter. 
A  temporary  fence  should  be  put  up  to  protect  the  young 
plants  from  injury,  and  the  fence  should  be  retained  until  the 
hedge  has  attained  sufficient  strength  to  require  its  protection 
no  longer — a  period,  under  favorable  circumstances,  of  three 
or  four  years  after  the  quicks  are  planted.  That  the  plants 
may  thrive  they  must  be  carefully  attended  to  at  first,  and  it 
is  essential  that  they  should  be  properly  cleaned  and  weeded 
at  least  twice  eveiy  year.  Once  every  year  toward  the  end 
of  the  summer  the  hedge  should  be  judiciously  trimmed,  not 
to  such  an  extent  as  to  produce  stunted  plants,  but  by  merely 
cutting  off  the  upper  and  more  straggling  shoots,  so  as  to 
bring  it  to  a  level  and  even  surface.  By  proceeding  in  this 
manner,  a  neat,  strong,  and  compact  hedge  of  healthy  plants 
will  be  obtained  in  about  three  years  after  planting." 

Trees,  however  much  they  may  add  to  the  picturesqueness 
of  a  road,  add  still  more  to  the  difficulty  of  keeping  it  in  repair; 
and  thick  avenues,  i.e.,  trees  planted  close  to  each 
other  on  both  sides  of  a  road,  are  quite  incom- 
patible with  the  due  preservation  of  the  surface.  The  evil  is 
worse  the  narrower  the  road  is,  for  then  very  little  sunshine 
can  get  to  the  road  at  all,  so  that  the  macadam  is  constantly 
damp  and  wears  away  much  more  rapidly  under  traffic. 


468 


THE  ART  OF  ROADMAKING 


Specification  for  Street 

Tree. 

The  tree  shall  be  a 
nursery-grown  tree  — 
sound,  straight  stem — 
clear  7-8  ft.  with  well- 
balanced  natural 
grown  head  on  top; 
roots  full  —  compact 
and  fibrous.  Such  roots 
afford  the  greatest 
amount  of  feeding 
function.  Pruning  and 
in  cutting — defer  till 
planting,  and  after- 
wards —  when  under 
proper  hands,  its  nat- 
ural form,  etc.,  may  be 
assured. 


"  As  to  the  desirability  of 
trees  on  roads  and  streets, 
some  claim  that  they  do 
more  harm  than  good ;  that 
they  impede  the  circulation 
of  the  air,  and  that,  as 
for  the  shade  they  afford, 
people  who  do  not  like 
sunshine  have  only  to  keep 
on  the  shady  side  of  the 
way ;  that  they  deprive  the 
road  surface  of  the  drying 
action  of  the  sun  and  air, 
and  that  in  wet  weather 
the  constant  dropping  of 
water  from  their  branches 
keeps  the  road  in  a  muddy 
state.  Others  claim  that 
trees,  especially  in  streets, 
temper  the  heat  and  serve 
as  a  protection  against 
dust,  that  the  evaporation 
from  their  leaves  tends  to  keep  the  sur- 
rounding air  cool  and  moist;  that  the 
perpetual  vibration  of  their  foliage  and 
swaying  of  their  branches,  whilst  admit- 
ting a  sufficient  amount  of  light,  serve 
to  protect  the  eyes  from  the  noonday 
glare;  that  they  act  as  disinfectants  by 
drawing  up  and  absorbing  the  organic 
matters  contained  in  the  filth  from  which 
the  streets  of  a  town  are  never  free  and 
which,  infiltrating  the  ground,  are  a  fre- 
quent cause  of  fevers  and  infection;  and 
it  is  asserted  that  on  soil 
roads  some  varieties  of 
trees  both  drain  the  road 
and  help  to  hold  its 
earthen  surface  together 
by  their  root  fibers."  * 

All  trees  that  are  orna- 
mental,   or    that     have 


FIG.  254. — SKETCH  OF  TYPE  OF  DESIRABLE  GENERAL 

CHARACTERISTICS  OF  A  YOUNG  TREE. 

iii  to  3  in.  in  diam. 


*  Byrne's  "Treatise  on  High- 
way Construction,"  p.  727. 


THE  ROADSIDE  469 

value  as  shade  trees,  should  be  preserved  and  protected, 
unless  they  grow  so  closely  that  they  make  too  dense  a 
shade.  In  hot,  dry  climates,  particularly,  and,  indeed,  in 
most  places,  trees  are  a  considerable  factor  in  reducing  the 
cost  of  maintenance,  since  they  lessen  the  evaporation  of  the 
moisture  from  the  macadam.  In  exposed  places  where  the 
sweep  of  the  wind  would  be  otherwise  unbroken,  they  serve  to 
prevent  in  a  measure  the  blowing  away  of  the  binder  from  the 
road  surface.  Unfortunately,  in  such  places  it  is  often  difficult 
to  make  trees  grow. 

Care  in  the  selection  of  the  kinds  of  trees  best  suited  to  the 
locality  is  important.  In  Massachusetts,  sugar,  Norway  and 
white  maples  and  American  elms  have  been  set  out  to  a  con- 
siderable extent  along  the  state  roads  with  satisfactory 
results.  These  trees  grow  fast  and  at  the  same  time  are 
fairly  long  lived. 

Trees  should  be  selected  with  reference  to  the  climate, 
locality,  quality  of  soil,  extent  of  space,  and  circumstances 
of  surroundings  in  general. 

Large-growing   varieties   should   be   selected   for 
places  of  great  extent,  smaller  varieties  for  places  of 
less  extent.     A  low  compact  tree  is  not  suitable  for  street 
planting. 

The  qualities  necessary  in  a  good  street  tree  are  that  it 
must  be  hardy,  must  not  be  affected  by  a  long-continued 
drought,  heat  must  not  wither  it  nor  make  it  look  rusty;  it 
must  be  able  to  withstand  dust,  smoke,  soot,  foul  air,  and  the 
insidious  attacks  of  insects,  and  be  able  to  recover  from  any 
malicious  or  accidental  injury  it  may  receive. 

The  tree  must  be  of  rapid  growth  and  develop  a  straight, 
clean,  stem  with  shady  foliage.  It  must  be  graceful  either 
in  full  leaf  or  when  bare,  as  in  winter;  its  roots  must  not 
require  too  much  room,  and  they  must  be  able  to  withstand 
the  effects  of  pollution  or  rough  treatment. 

Whatever  variety  of  tree  is  selected,  the  following  precautions 
should  be  taken  to  insure  its  flourishing: 

1.  The  young  tree  should  have  been  well  nourished  in  the 
nursery;  it  should  nat  be  planted  on  the  street  until  its  stem 


470  THE  ART  OF  ROADMAKING 

is  over  8  feet  in  height  and  about  3  inches  in  diameter.  The 
stem  should  be  clean  and  straight,  and  the  whole  tree  sym- 
metrical. 

2.  The  ground  where  a  tree  is  to  be  set  should  be  suitable 
for  tree  growth.  If  it  is  not,  all  poor  material  should  be 
removed  and  good  soil  substituted.  The  amount  to  be  re- 
moved depends  upon  circumstances  and  can  be  determined 
by  examination.  A  tree  to  nourish  must  have  plenty  of  good 
ground  in  which  to  grow;  it  should  be  good  to  the  depth  of  at 
least  3  feet,  and  an  equal  distance  in  all  directions  from  the 
trunk  when  practicable.  The  amount  of  good  soil  is  of  greater 
importance  than  the  shape  it  is  in.  The  further  the  tree  is 
planted  from  the  curb  the  better,  so  as  not  only  to  give  it  a 
larger  body  of  soil,  but  to  lessen  the  risk  of  killing  the  tree 
by  the  pollution  of  the  ground  with  gas  from  defective  pipes 
and  also  excess  of  moisture  from  the  gutters. 

Trees  should  be  placed  so  far  from  one  another  that  at 
maturity  they  will  not  meet.  Such  distances  will  enable  them 
to  develop  in  their  natural  beauty.  To  determine 
the  proper  distance  apart  measure  the  spread  of 
full-grown  trees  of  the  same  variety  as  those  to  be  planted; 
it  will  vary  from  30  to  50  feet.  The  trees  should  alternate 
on  opposite  sides  of  the  street.  Where  streets  cross  at  right 
angles  or  nearly  so,  two  trees  of  large-growing  varieties  may  be 
placed  on  each  corner,  far  enough  from  the  corner  of  the  curb 
not  to  interfere  with  the  catch-basin  when  there  is  one.  Each 
tree  should  be  placed  on  the  tree  line  of  one  street  and  the 
fence  line  of  the  other;  this  will  require  eight  trees  to  every 
intersection.  The  trees  so  planted  should  form  a  handsome 
mass  of  foliage  and  afford  an  agreeable  shade  where  most 
needed.  At  some  intersections  it  may  not  be  possible  to  plant 
all  the  eight  trees,  but  as  many  as  can  should  be  placed. 
Each  tree  should  be  protected  with  a  light  iron  railing  to 
prevent  damage  to  the  trunk  from  cutting  or  otherwise. 

A  good  arrangement  along  roadsides  for  trees  with  large 
tops  is  to  set  them  about  50  feet  apart  on  each  side,  but 
alternated  so  that  there  be  a  tree  for  every  25  feet  along  the 
road. 


THE   ROADSIDE  471 

The  Tree-planting  Association  of  New  York  *  has  endeavored 
to  interest  property  owners  to  plant  street  trees  in  the  city 
streets,   etc.,   and,   despite  lack   of   cooperation   on   the   part 
of  the   city  authorities,   it  has  had  some  success. 
Several  years  ago  the  Tree-planting  Law  passed  the  Tree~ 
legislature,  by  which  the  control  of  street  planting  Association 
and  the  care  of  existing  trees  outside  of  the  parks, 
was   placed   under   the   park   commissioner.     The   conditions 
prescribed  by  the  park  department  under  which  tree  planting 
must   be   carried   on   in   the   city   embody   many  restrictions 
which   tend   to   discourage   the   enterprising   property   owner 
in  the  work  of  adorning  and  improving  his  own  property  and 
benefiting  his  neighbor  and  the  public  at  the  same  time. 

City  trees  in  New  York  are  limited  in  varieties  by  the  park 
department  to  the  maples,  the  elms,  the  planes,  the  lindens — 
pin  oak  mainly.  The  poplars  (the  Cardicia  poplar  in  some 
respects  quite  desirable)  are  interdicted.  Of  the  maples,  the 
Norway,  sugar,  white,  scarlet,  etc.;  of  the  elm,  the  English, 
American  (most  graceful  of  tree  form),  the  Dutch,  the  Hunting- 
don; of  the  lindens,  the  American  or  European,  etc.  The 
Cardicia  poplar  is  a  lusty,  quick  grower  with  clear  bright 
foliage  seldom  afflicted  with  insects,  but  ages  early  and  the 
wood  is  brittle.  Trees  like  the  sugar  maple,  the  American 
elms,  the  plane,  require  the  wrider  roadways,  as  too  much 
.  incutting  spoils  characteristic  growth  of  the  larger  trees. 
In  the  city,  one  of  the  requirements  as  to  pit  is  almost  pro- 
hibitory, namely,  soil  equal  to  3  cubic  yards.  It  is  difficult 
to  provide  such  an  exacvation  in  many  places  and  with  the 
necessary  soil,  and  the  usual  opening  in  the  flagging  or  con- 
crete walk  of  a  round  or  square  space,  brings  up  the  cost  of  the 
tree,  the  planting,  and  the  ground  to  between  from  $22  to  $30. 

*  Secretary,  Joseph  L.  Delafield,  35  Nassau  Street,  New  York  City. 


APPENDIX  I 

SPECIFICATIONS   AND   CONTRACTS* 

Between  the  individual  or  corporation  desiring  the  work  done  and 
the  contractor  who  performs  it,  stands  the  engineer  who  has  designed 
it  and  who  usually  superintends  its  execution.  He  is  in  the  employ 
of  the  persons  promoting  the  enterprise,  and  it  devolves  upon  him  to 
make  sure  that  those  who  retain  him  receive  an  honest  and  fair  return 
for  their  money. 

In  order  that  the  contractor  may  understand  the  scope  of  the  work 
to  be  performed  and  the  details  of  its  construction,  written  descriptions 
and  plans  more  or  less  complete,  defining  the  methods  of  construction, 
material,  etc.,  to  be  used,  are  prepared  by  the  engineer  for  the  approval 
of  the  company  having  the  work  done  and  for  the  guidance  of  the  con- 
tractor. These  written  documents  are  the  Specifications,  and  together 
with  the  Contract,  of  which  they  form  a  part,  they  fix  definitely  the 
relations  that  shall  subsist  between  the  company  or  corporation  and 
the  contractor. 

No  matter  how  simple  a  structure  may  be,  there  must  be  a  plan,  if 
it  is  to  be  constructed  intelligently  and  efficiently.  As  the  size  and 
importance  of  the  structure  increase,  the  plan  becomes  more  and  more 
complex,  and  hence  the  greater  necessity  for  putting  it  in  some  fixed 
and  definite  form  which  conveys  the  exact  idea  existing  in  the  mind  of 
the  engineer.  To  secure  the  proper  execution  of  the  work  of  any  magni- 
tude, specifications  are  absolutely  necessary,  and  they  should  be  prepared 
with  great  care  and  exactness.! 

Theoretically,  three  general  classes  of  engineering  specifications  may 
be  noted.  In  the  first  the  aim  of  the  engineer  is  to  specify  the  end  or 
result  that  it  is  desired  to  secure,  leaving  the  contractor  free  to  originate 
and  follow  the  methods  by  which  these  results  are  to  be  attained.  In 
the  second  the  engineer  aims  to  secure  the  desired  end,  by  specifying  in 


*  Condensed  from  Waddell  and  Wait's  "Specifications  and  Contracts,"  and  Whinery's 
41  Specifications  for  Roads,  Streets,  and  Pavements." 

t  In  addition  to  their  value  as  memoranda  and  aids  in  preparing  specifications 
for  a  particular  project,  carefully  prepared  general  specifications,  embodying  the 
latest  approved  practice,  sometimes  supply  the  must  useful  and  acceptable  brief 
treatises  upon  any  particular  branch  of  engineering  work. 

473 


474  THE  ART  OF  ROADMAKING 

detail  the  materials  and  the  methods  which  in  his  opinion  will  accomplish 
the  purpose,  he  himself  assuming  responsibility  for  the  results.  Either 
of  these  two  classes  of  specifications  is  permissible,  and  the  engineer  may 
choose  the  one  which  in  his  opinion  seems  best  adapted  to  the  character 
of  the  work  to  be  done,  and  the  conditions  under  which  it  must  be 
prosecuted. 

In  the  third  class  of  specifications,  met  with  more  frequently  than 
they  should  be,  the  engineer  undertakes  to  prescribe  not  only  the  char- 
acter of  the  materials  to  be  used  and  the  methods  to  be  pursued,  but  also 
the  results  to  be  attained.  The  position  thus  assumed  is  illogical,  and 
often  unreasonable,  and  may  lead  to  complications  between  the  engineer 
and  the  contractor.  If  a  contractor  be  required  to  turn  out  a  product 
which  shall  conform  to  certain  standards,  he  may  properly  be  given 
much,  if  not  full,  latitude,  as  to  how  the  stipulated  results  shall  be  secured, 
and  may  be  held  fully  responsible  for  the  outcome;  if  on  the  other  hand 
the  engineer  chooses  to  specify  with  more  or  less  minuteness  the  character 
of  the  materials  to  be  used  and  the  methods  of  construction  to  be  followed, 
and  enforces  compliance  therewith,  it  seems  fair  and  just  that  he  should 
assume  responsibility  for  the  results  produced,  and  therefore  unfair  to 
hold  the  contractor  to  responsibility  for  consequences  arising  from  the 
use  of  materials  and  methods  which  he  was  allowed  no  choice  or  latitude 
in  selecting. 

In  street  paving  work,  of  well  known  and  standard  character,  the 
second  class  of  specifications  seems  preferable  for  a  number  of  reasons, 
the  leading  one  being  that  the  time  required  to  develop  the  good  or  bad 
quality  of  the  work  must  usually  exend  over  a  considerable  number 
of  years,  and  the  conditions  to  which  the  pavement  may  be  subjected 
in  the  meantime  are  likely  to  vary  so  widely  that  it  may  be  very  difficult, 
if  not  impossible,  to  prescribe  a  satisfactory  standard  of  service  and 
endurance.  Disputes  are  therefore  liable  to  arise  between  the  munici- 
pality and  the  contractor  as  to  the  latter's  liability,  or  conditions  may 
make  it  difficult  or  impossible  to  hold  the  contractor  to  strict  account 
for  that  liability. 

For  convenience  of  reference  and  for  clearness,  specifications  are  usually 
divided  into  clauses,  which  may  be  classed  as  "general"  and  " specific." 
General  clauses  refer  to  the  business  relations  that  shall  exist  between 
the  parties  to  the  contract.  In  them  is  found  the  general  description 
of  the  work  as  a  whole  without  any  particular  reference  to  details.  Times 
and  methods  of  making  payments,  adherence  to  specifications,  inspection, 
and  other  analogous  headings  make  up  their  subject  matter.  They 
should  be  comprehensive  in  their  scope,  and  should  not  contradict  one 
another.  It  is  well  to  avoid  a  double  description  of  any  particular 
thing,  as  contradictory  clauses  are  sure  to  be  a  stumbling  block  that 
will  create  friction  and  cause  delay.  At  first  glance  one  would  say  that 
such  clauses  are  easily  eliminated,  but  care  is  necessary  to  accomplish 
this. 


SPECIFICATIONS  AND  CONTRACTS  475 

Specific  clauses  have  to  do  with  the  details  of  construction  and  the 
description  of  the  particular  features  of  design.  They  embody  the  special 
ideas  that  the  engineer  wishes  to  incorporate  in  the  work,  and  they  should 
be  just  as  minute  in  detail  as  is  requisite  to  set  forth  the  exact  plan 
desired.  Detailed  drawings  may  be  necessary  to  indicate  clearly  just 
what  is  to  be  done,  and  these  drawings  either  should  be  prepared  before 
the  specifications  are  written,  or  at  least  should  be  sufficiently  matured 
in  the  mind  of  the  engineer  to  enable  him  to  write  his  specifications  in 
accordance  with  them. 

The  ideal  specification  is  one  that  furnishes  a  wholly  sufficient  guide 
to  the  accomplishment  of  the  desired  purpose;  that  provides  for  every 
possible  contingency  which  may  arise,  and  is  couched  in  language  which 
not  only  means  exactly  what  it  was  intended  to  mean,  but  is  incapable 
of  any  other  interpretation.  It  is  needless  to  say,  however,  that  no 
example  of  such  a  specification  can  be  instanced  as  a  model,  as  the 
engineer  is,  in  common  with  all  men,  fallible,  and  he  can  hardly  hope, 
in  the  preparation  of  specifications,  to  make  them  perfect;  to  cover 
every  item  and  particular;  or  to  escape  some  ambiguities  of  expression, 
and  some  degree  of  indefiniteness. 

Specifications  should  look  to  the  accomplishment  of  an  end  rather 
than  to  the  means  of  its  attainment,  and  it  must  be  remembered  that 
under  these  circumstances  the  contractor  cannot  be  held  responsible 
for  the  mistake  of  the  engineer. 

The  specifications  form  a  part  of  the  contract,  and  when  the  latter  is 
signed,  the  contractor  agrees  to  all  the  conditions  they  set  forth.  It  is 
proper  to  assume  that  he  has  read  the  specifications  and  is  familiar  with 
their  requirements,  and  he  signs  the  contract  and  makes  his  bond  with 
the  full  knowledge  of  what  is  before  him. 

The  dividing  line  between  the  specifications  and  contracts  is  most 
difficult  to  draw,  for  in  any  particular  case  two  engineers  will  rarely 
agree  as  to  what  clauses  pertain  properly  to  the  specifications  and  what 
to  the  contract.  The  preference  is  to  throw  as  much  of  the  matter  as 
possible  into  the  specifications  and  reduce  the  size  of  the  contract  proper 
to  a  minimum,  avoiding  repetition  of  statement  in  the  two  parts  of  the 
work,  but  of  necessity  treating  certain  subjects  in  both  parts,  though 
from  different  point  of  view.  All  clauses  that  relate  to  methods  of 
construction,  qualities  of  materials,  character  of  the  work,  rules  limiting 
the  functions  and  powers  of  the  contractor  and  defining  the  authority 
of  the  engineer,  directions  to  bidders,  and  transportation  of  men  and 
materials,  unquestionably  belong  to  the  specifications;  alterations  of 
plans,  damages,  extras,  payments,  responsibility  for  accidents,  the 
spirit  of  the  specifications,  strictness  of  inspection,  liquidated  damages, 
scope  of  the  contract,  and  time  of  completion  might  perhaps  be  properly 
inserted  in  either  division,  but  it  is  customary  to  include  all  of 
these  clauses  and  others  of  like  character  and  scope,  in  the  specifica- 
tions. 


476  THE  ART  OF  ROADMAKING 

The  following  general  clauses  and  enumeration  of  specific  clauses, 
will  give  an  idea  of  the  ground  covered  by  a  thorough  set  of  specifications:* 

FOR  GRADING  AND  PAVING,  OR  REPAYING 

with Pavement . 

on  a Foundation,  the  Roadway 

of 

Street,  from 

to 

together  with  all  work  incidental  thereto. 

GENERAL  DESCRIPTION  OF  WORK.  The  work  embraced  in  and  to  be 
done  under  this  contract  consists  of  grading  the  entire  street  from  curb 
to  curb  between  the  limits  named,  including  the  removal  or  readjust- 
ment of  the  pavement  now  on  the  roadway,  setting  and  resetting  curbing, 
laying  or  relaying  sidewalks  where  required,  furnishing  all  new  material 
and  performing  all  the  labor  required  for  paving  the  roadway,  together 
with  all  incidental  work  necessary  to  complete  the  whole  in  a  proper 
manner,  in  accordance  with  the  contract,  the  plans  on  file  in  the  office 
of  the  city  engineer,  these  specifications  and  the  instructions  of  the  city 
engineer,  herein  referred  to  as  the  engineer,  or  his  authorized  agents. 

REFERENCES.  The  numbered  divisions  of  these  specifications  are 
herein  designated  as  "sections,"  each  being  referred  to  by  the  number 
standing  at  its  beginning. 

The  plans  and  drawings  relating  to  this  work,  on  file  in  the  office  of 
the  city  engineer  are  designated  as 

AUTHORITY.  1.  Wherever,  in  these  specifications,  the  words,  the  City, 
are  used,  they  shall  be  understood  to  refer  to  the  duly  constituted  munici- 
pal government  of  the  city  of 

or  its  authorized  agents,  acting  within  the  authority  specifically  conferred 
upon  them  by  the  said  municipal  government.! 

Wherever,  in  these  specifications,  the  words,  the  engineer,  shall  be 
used,  they  shall  be  understood  to  refer  to  the  city  engineer  of  said  city, 
or  his  deputies  or  assistants  acting  within  the  authority  conferred  upon 
them  by  the  city  engineer. 

But  no  agent  of  the  city  shall  have  power  to  revoke,  alter,  enlarge 
or  relax  the  stipulations  or  requirements  of  these  specifications,  except 
in  so  far  as  such  authority  may  be  specifically  conferred  in  or  by  the 
specifications  themselves,  without  the  formal  authorization  so  to  do, 
conferred  by  ordinance,  resolution  or  other  usual  official  action  of  the 
city.J 

INTERPRETATION.  2.  In  case  of  any  actual  or  alleged  disagreement 
or  discrepancy  between  the  contract,  these  specifications,  and  the  plans 
for  the  work  on  file  in  the  office  of  the  engineer,  the  language  and  pro- 
visions of  the  contract  shall  take  precedence  and  prevail;  and  the  engineer 

*  From  "General  Specifications  for  Roads,  Streets,  and  Pavements,"  by  S.  Whinery, 
1907. 

t  In  specifications  to  be  used  in  any  particular  city  the  official  name  of  the  city 
government,  as  the  City  Council,  the  Commissioners  of  Public  Works,  etc.,  should 
be  used  instead  of  this  general  designation. 

J  Such  a  proviso  as  this  seems  proper  in  justice  to  both  the  city  engineer  and  the 
contractor;  the  former  should  not  be  held  repsonsible  for  the  acts  of  his  assistants 
when  they  should  transcend  the  authority  conferred  upon  them,  and  the  latter  should 
be  put  upon  his  guard  with  reference  to  requirements  which  he  is  not  satisfied  are 
sanctioned  or  approved  by  the  city  engineer. 


SPECIFICATIONS  AND  CONTRACTS  477 

shall  determine  in  each  case  whether  the  specifications  or  the  plans  shall 
be  followed. 

QUALITY  OF  MATERIAL  AND  WORK.  3.  The  judgment  and  decision 
of  the  engineer  as  to  whether  the  materials  supplied  and  the  work  done 
under  this  contract  comply  with  the  requirements  of  these  specifications, 
shall  be  conclusive  and  final.  No  material  shall  be  used  in  the  work 
until  it  has  been  examined  and  approved  by  the  engineer,  or  his  author- 
ized agents.  All  rejected  material  must  be  promptly  removed  from 
the  work  and  replaced  with  that  which  is  acceptable  to  the  engineer, 
and  all  improper  or  defective  work  must  be  corrected,  and,  if  necessary, 
removed  and  reconstructed  so  as  to  comply  with  these  specifications 
and  the  instructions  of  the  engineer. 

INSPECTION.  4.  The  engineer  may  provide  for  the  inspection,  by 
assistants  and  inspectors  under  his  direction,  of  all  materials  used  and 
all  work  done  under  this  contract.  Such  inspection  may  extend  to  all 
or  any  part  of  the  work,  and  to  the  preparation  or  manufacture  of 
materials  to  be  used,  whether  within  the  limits  of  the  work  on  the  street, 
or  at  any  other  place.  The  engineer  and  his  inspectors  shall  have  free 
access  to  all  parts  of  the  work,  including  mines,  quarries,  manufactories, 
or  other  places  where  any  part  of  the  materials  to  be  used  is  procured, 
manufactured  or  prepared.  The  contractor  shall  furnish  the  engineer 
all  information  relating  to  the  work  and  the  material  therefor  which 
the  engineer  may  deem  necessary  or  pertinent,  and  with  such  samples 
of  materials  as  may  be  required.  The  contractor  shall,  at  his  expense, 
supply  inspectors  with  such  labor  and  assistance  as  may  be  necessary 
in  the  handling  of  materials  for  proper  inspection.  Inspectors  shall 
have  authority  to  reject  defective  material  and  to  suspend  any  work 
that  is  being  improperly  done,  subject  to  the  final  decision  of  the  engineer. 
Inspectors  shall  have  no  authority  to  permit  deviations  from,  or  to 
relax  any  of  the  provisions  of  these  specifications  without  the  written 
permission  or  instruction  of  the  engineer;  nor  to  delay  the  contractor 
by  failure  to  inspect  materials  and  work  with  reasonable  promptness. 

The  payment  of  any  compensation,  whatever  may  be  its  character 
or  form,  or  the  giving  of  any  gratuity,  or  the  granting  of  any  valuable 
favor,  by  the  contractor  to  any  inspector,  directly  or  indirectly,  is  strictly 
prohibited,  and  any  such  act  on  the  part  of  the  contractor  will  constitute 
a  violation  of  these  specifications.* 

INJURIES  TO  PERSONS  AND  PROPERTY.  5.  The  contractor  shall  be 
held  alone  responsible  for  all  injuries  to  persons,  and  for  all  damages 
to  the  property  of  the  city  or  others,  caused  by  or  resulting  from  the 
negligence  of  himself,  his  employees  or  agents,  during  the  progress  of, 
or  connected  with  the  prosecution  of  the  work,  whether  within  the  limits 
of  the  work,  or  elsewhere.  He  must  restore  all  injured  property,  including 
sidewalks,  curbing,  sodding,  pipes,  conduits,  sewers  and  other  public 
or  private  property  to  a  condition  as  good  as  it  was  when  he  entered 
upon  the  work. 

SANITARY  CONVENIENCES;    NUISANCES.     6.  The  contractor  shall  pro- 

*  It  may  be  objected  that  this  requirement  is  unusual  and  unnecessary,  since  such 
practices  are  recognized  as  wrong,  and  as  presumptive  of  fraud  and  malpractice  on 
the  part  of  both  of  the  contractor  and  the  inspector.  It  cannot,  however,  be  denied 
that  in  many  cities  such  means  are  employed  by  contractors  to  unduly  inflence  the 
action  of  inspectors  and  that  not  infrequently  the  latter  not  only  accept,  but  per- 
sistently demand,  valuable  considerations  from  the  contractor.  Silence  of  the 
specifications  on  this  point  cannot,  of  course,  be  construed  into  consent,  but  there 
is  no  good  reason  for  the  silence.  There  should  be  left  no  excuse  for  misconception 
of  the  position  of  the  city  or  of  the  engineer  upon  this  point. 


478  THE  ART  OF  ROADMAKING 

vide  all  necessary  privy  accommodations  for  the  use  of  his  employees 
on  the  street,  and  shall  maintain  the  same  in  a  clean  and  sanitary  con- 
dition. He  shall  not  create  nor  permit  any  nuisance  to  the  public  or 
to  residents  in  the  vicinity  of  the  work. 

PUBLIC  CONVENIENCE.  7.  No  material,  or  other  obstruction  shall 
be  placed  within  five  feet  of  fire  hydrants,  which  must  be  at  all  times 
readily  accessible  to  the  fire  department. 

During  the  progress  of  the  work  the  convenience  of  the  public  and  of 
the  residents  along  the  street  must  be  provided  for  as  far  as  practicable. 
Convenient  access  to  driveways,  houses  and  buildings  along  the  street 
must  be  maintained  wherever  possible.  Temporary  approaches  to 
and  crossings  of  intersecting  streets  and  sidewalks  must  be  provided 
and  kept  in  good  condition,  wherever  practicable. 

BARRIERS,  LIGHTS,  WATCHMEN.  8.  The  contractor  shall  provide 
and  maintain  such  fences,  barriers,  " street  closed"  signs,  reel  lights, 
and  watchmen  as  may  be  necessary  to  prevent  avoidable  accidents  to 
residents  and  to  the  public. 

DISORDERLY  EMPLOYEES.  9.  Disorderly,  intemperate,  or  incompetent 
persons  must  not  be  employed,  retained,  or  allowed  upon  the  work. 
Foremen  or  workmen  who  neglect  or  refuse  to  comply  with  the  instruc- 
tions of  the  engineer,  shall,  at  his  request,  be  promptly  discharged,  and 
shall  not  thereafter  be  re-employed  without  his  consent. 

ORDER  AND  PROGRESS  OF  DOING  WORK.  10.  The  work  under  this 
contract  shall  be  prosecuted  at  as  many  different  points,  at  such  times, 
and  in  such  sections  along  the  line  of  the  work,  and  with  such  forces  as 
the  engineer  may  from  time  to  time  deem  necessary,  and  direct,  to 
secure  its  completion  within  the  contract  time.  Not  more  than  one 
thousand  (1,000)  linear  feet  of  the  street  shall  be  torn  up,  obstructed  or 
closed  to  travel  at  any  one  time  without  the  written  permission  of  the 
engineer.  Completed  portions  of  the  pavement  shall  be  opened  to 
travel  as  directed  by  the  engineer,  but  such  opening  shall  not  be  construed 
as  an  acceptance  by  the  City  of  the  work  done.  Where  thus  opened  to 
public  travel  by  the  direction  of  the  engineer,  the  contractor  will  not 
be  held  responsible  for  injuries  to  the  work  caused  by  such  travel  or 
public  use,  pending  the  final  completion  and  acceptance  of  the  whole 
work. 

MEASUREMENT  AND  ESTIMATES.  11.  Final  estimates  will  be  based 
upon  the  actual  quantities  of  completed  and  accepted  work,  customary 
or  conventional  methods  of  measurement  and  computation  to  the  con- 
trary notwithstanding. 

GRADE  AND  CONTOUR  OF  PAVEMENT.  12.  Roadway  pavements  shall 
be  laid  to  such  grades,  crown  and  contour  of  surface  as  the  plans  may 
show  or  the  engineer  may  direct,  and  the  surface  of  the  completed  pave- 
ment shall  conform  accurately  to  such  grades,  crown  and  contour.  The 
designed  surface  of  the  completed  pavement  shall  be  considered  as  the 
datum  or  plane  of  reference  in  fixing  the  location  or  level  of  the  sub- 
grade,  of  the  pavement  foundation,  and  of  structures  connected  there- 
with. It  will  be  hereafter  referred  to  in  these  specifications  as  "  the 
pavement  datum." 

CITY  MONUMENTS  OR  STAKES.  13.  The  contractor  must  carefully 
protect  from  disturbance  or  injury  all  city  monuments,  stakes  and  bench- 
marks, and  shall  not  excavate  nearer  than  five  feet  to  any  of  them 
without  the  permission  of  the  engineer;  or  until  they  have  been  removed, 
witnessed,  or  otherwise  disposed  of  by  the  engineer. 

OLD  MATERIAL.  -  14.  All  material  or  structures  removed  from  the 
street  and  not  required  for  the  new  construction,  but  which  the  city 
may  desire  to  reserve,  shall  be  delivered  and  neatly  piled  up  in  a  corpora- 


SPECIFICATIONS  AND  CONTRACTS  479 

tion  yard  or  elsewhere,  by  the  contractor,  as  the  engineer  may  direct. 
Such  reserved  material  shall  be  considered  in  the  custody  of  the  contractor 
until  delivered  at  the  place  designated,  and  he  will  be  held  responsible 
for  its  care  and  protection,  and  must  make  good  any  losses  occasioned 
by  damage,  theft,  or  misappropriation  while  it  is  on  the  street  or  en 
route  to  the  place  of  storage.  If  the  contractor  shall  be  required  to  haul 
such  reserved  material  more  than  one-half  mile,  he  shall  be  paid  a  reason- 
able price,  to  be  agreed  upon  in  advance,  for  the  haul  exceeding  that 
distance. 

Material  taken  from  the  work  which  is  to  be  used  in  the  new  construc- 
tion shall  be  compactly  piled  where  it  will  least  obstruct  the  sidewalks 
or  adjoining  sections  of  the  street,  and  properly  protected  by  the  contractor 
until  it  is  required  for  use. 

All  old  material  removed  from  the  work,  including  the  material  excavated 
in  preparing  the  sub-grade,  not  reserved  by  the  city  nor  to  be  used  again 
in  the  work,  shall  belong  to  the  contractor  and  must  be  removed  by  him 
from  the  street  as  promptly  as  possible.  It  must  not  be  placed  on  the 
sidewalks  or  adjacent  streets,  nor  on  any  other  street  or  property  belong- 
ing to  the  city,  nor  on  the  property  of  private  owners,  without  the  written 
consent  of  the  engineer,  or  the  owner  of  the  property. 

STORAGE  OF  NEW  MATERIAL.  15.  The  material  for  construction  when 
brought  upon  the  street  shall  be  neatly  piled  so  as  to  cause  as  little 
obstruction  to  travel  as  possible,  and  so  that  it  may  be  conveniently 
inspected. 

REBUILDING  AND  ADJUSTING  STREET  STRUCTURES.  16.  Catch  basins, 
manhole,  sewer  and  water  frames  and  covers,  sewer  inlets,  water  pipes 
and  other  conduits,  belonging  to  the  city  and  within  the  limits  of  the  work, 
shall,  if  necessary,  be  reset  to  the  new  lines  and  grades  of  the  street  and 
for  this  purpose  good  brick  masonry  of  the  original  thickness,  laid  in 
Portland  cement  mortar  shall  be  used.  Great  care  must  be  taken  to 
set  all  such  structures  as  project  through  the  pavement  exactly  to  the 
grade  and  contour  of  the  new  street  surface,  and  any  defects  in  the 
conformity  of  such  structures  to  the  pavement  datum,  discovered  at  the 
time,  or  during  the  progress  of  the  work,  or  during  the  guaranty  period, 
stipulated  in  Sec.  108,*  shall  be  promptly  remedied  by  the  contractor. 

NOISELESS  MANHOLE  COVERS.  17.  Asphalt-filled  noiseless  covers, 
complete,  for  water  and  sewer  manholes,  of  approved  design,  shall  be 
furnished  and  set  by  the  contractor  wherever  directed  by  the  engineer. 
They  shall  be  made  according  to  general  plans  and  details  furnished 
by  the  engineer,  and  of  such  dimensions  as  to  properly  fit  their  frames. 

CLEAN  SIDEWALKS.  18.  During  the  progress  of  the  work,  the  side- 
walks and  portions  of  the  street  adjoining  the  work,  or  in  its  vicinity, 
must  not  be  obstructed  or  littered  more  than  may  be  absolutely  necessary, 
and  the  adjacent  sidewalks  must  be  kept  clean. 

FINAL  CLEANING  UP.  19.  Immediately  after  the  completion  of  the 
work  or  any  consecutive  portion  of  it,  the  contractor  shall  remove  from 
it  all  unused  material,  refuse  and  dirt  placed  by  him  on  or  in  the  vicinity 
of  the  work,  or  resulting  from  its  prosecution,  and  restore  the  street  to 
a  condition  as  clean  as  before  the  work  was  begun;  and  the  new  pave- 
ment shall  be  properly  cleaned. 

INCIDENTAL  WORK  AT  CONTRACTOR'S  EXPENSE.  20.  All  the  work 
to  be  done  by  the  contractor,  specified  and  enumerated  in  sections  3  4 
5,  6,  7,  8,  10,  11,  12,  13,  14,  15,  16,  17,  18  and  19,  as  well  as  any  minor 
details  of  work  not  specifically  mentioned  in  the  .specifications,  but 
obviously  necessary  for  the  proper  completion  of  the  work,  shall  be 

*  See  page  481. 


480  THE  ART  OF  ROADMAKING 

considered  as  incidental,  and  as  being  a  part  of  and  included  with  the 
work  for  which  prices  are  named  in  the  contract.  The  contractor  will 
not  be  entitled  to  any  extra  or  additional  compensation  therefor. 

EXTRA  WORK.  21.  The  city  may  require  the  contractor  to  furnish 
such  additional  materials  and  to  do  such  additional  work,  not  provided 
for  in  the  contract  and  these  specifications,  but  which  may  be  found 
necessary  or  pertinent  to  the  proper  prosecution  and  completion  of  the 
work  embraced  in  the  contract,  at  prices  to  be  agreed  upon  in  writing, 
in  advance.  But  no  work  other  than  that  included  in  the  contract  and 
these  specifications  and  which  is  covered  by  and  to  be  paid  for  at  the  prices 
named  in  the  contract,  shall  be  done  by  the  contractor  except  upon  a 
written  order  from  the  engineer.  In  the  absence  of  such  written  order 
from  the  engineer  the  contractor  will  not  be  entitled  to  payment  for  any 
such  additional  or  extra  work. 

CURBING  TO  BE  COMPLETED  IN  ADVANCE.  22.  The  setting  of  all  new 
curbing  and  guttering  and  the  redressing,  resetting  or  readjustment  of 
all  old  curbing  must  be  completed  at  least  100  feet  in  advance  of  the 
construction  of  the  street  foundation. 

PREPARING  THE  SUB- GRADE.  23.  The  whole  area  to  be  occupied  by 
the  pavement  and  its  foundation  shall  be  excavated  to  a  sub-grade  at 
such  a  depth  that  after  being  compacted  by  the  roller,  the  surface  will 

be  inches  below  the  pavement  datum,  and  truly  parallel 

thereto.  In  excavating,  the  earth  must  not  be  disturbed  below  the 
sub-grade.  Plowing  will  not  be  permitted  where  the  depth  of  earth  to 
be  removed  is  less  than  six  (6)  inches,  and  in  no  case  must  the  plow  be 
allowed  to  penetrate  to  within  less  than  one  inch  of  the  sub-grade. 
Places  that  are  found  to  be  loose,  or  soft,  or  composed  of  unsuitable 
material,  below  sub-grade,  must  be  dug  out  and  refilled  with  sand,  or 
other  material  as  good  as  the  average  of  that  found  on  the  street.  After 
the  excavation  is  completed  and  the  surface  neatly  trimmed,  the  whole 
area  shall  be  well  compacted  by  rolling  with  a  roller  weighing  not  less  than 
five  tons.  Areas  inaccessible  to  the  roller  shall  be  rammed  until  they 
are  as  well  compacted  as  the  rolled  surface.  When  the  rolling  is  completed 
the  surface  must  be  nowhere  more  than  three-fourths  inch  below,  nor 
more  than  three-eighths  inch  above  the  true  sub-grade.  If,  after  the 
rolling  is  completed  and  before  the  pavement  foundation  is  laid,  the 
surface  shall  become  disturbed  in  any  way,  it  must  be  replaced  and  properly 
compacted. 

Where  the  natural  surface  of  the  ground  shall  be  below  the  sub-grade, 
or  shall  become  so  by  the  removal  of  old  pavement  or  other  structures, 
it  must  be  filled  to  the  sub-grade  in  layers  not  exceeding  five  inches  in 
depth,  and  each  layer  shall  be  thoroughly  rolled  or  rammed  before  the 
next  layer  is  placed  upon  it,  and  when  the  filling  is  completed  the  filled 
area  must  be  properly  trimmed  and  compacted  by  rolling  or  ramming 
to  the  true  sub-grade,  as  in  excavation.  The  material  excavated  from 
the  street  may  be  used  for  such  filling,  provided  it  be  of  suitable  quality. 
Where  it  cannot  be  thus  procured  from  the  street  it;  must  be  obtained 
by  the  contractor  elsewhere,  in  which  case  the  actual  quantity  so  obtained, 
measured  after  it  is  compacted  in  the  street,  will  be  paid  for  at  the 
contract  price  for  "earth  filling."  The  price  bid  for  "earth  excavation" 
will  be  paid  for  all  material  excavated  above  the  sub-grade,  measured 
in  place  on  the  street,  which  price  includes  the  cost  of  disposing  of  the 
excavated  material,  whether  as  waste  or  filling,  and  of  trimming  and 
rolling  or  ramming  the  sub-grade,  and  of  making  it  ready  for  the  pave- 
ment foundation. 

Where  the  soil  composing  the  sub-foundation  is  found  to  be  wet  or 
"springy,"  a  system  of  soft  tile  drains,  discharging  into  the  street  drainage 


SPECIFICATIONS  AND  CONTRACTS  481 

system,  shall  be  constructed  by  the  contractor,  as  directed  by  the 
engineer.  The  tile  shall  be  laid  in  trenches  about  one  foot  wide  and 
from  one  to  two  feet  deep.  After  the  tile  is  in  place  the  trenches  shall 
be  filled  with  compacted  crushed  stone  or  gravel.  The  tile  will  be  paid 
for  at  the  contract  prices  for  the  same,  which  shall  include  the  cost  of 
excavating  and  filling  the  trenches. 

Then  follow  specific  clauses  covering  all  details  in  regard  to  foundations, 
laying  the  pavement,  etc.;  according  to  the  special  form  of  structures  used. 

GUARANTY.*  24.  The  contractor  shall  guarantee  that  all  the  materials 
used  and  all  the  work  done  under  this  contract  shall  fully  comply  with 
the  requirements  of  these  specifications,  the  plans  hereinbefore  referred 
to  and  the  instructions  of  the  engineer.  Any  defects  in  the  completed 
work,  or  any  part  of  it,  or  any  failure  of  the  work  to  fully  perform  or  endure 
the  service  for  which  it  was  intended,  which,  in  the  opinion  of  the  engineer, 
are  attributable  to  the  use  of  materials,  skill,  or  workmanship  not  in 
compliance  with  the  said  specifications,  plans  and  instructions,  that  may 

appear  in  the  work,  or  any  part  of  it,  within  a  period  of 

years  after  the  date  of  the  certificate  of  completion  and  acceptance,  shall 
be  regarded  as  prima  facie  and  conclusive  evidence  that  the  contractor 
has  failed  to  comply  with  the  said  specifications,  plans  and  instructions. 
And  the  contractor  shall,  at  his  own  expense,  at  such  time  and  in  such 
manner  as  the  engineer  may  direct,  repair  or  take  up  and  reconstruct 
any  such  defective  work,  in  full  compliance  with  the  original  specifications, 
plans  and  instructions.  And  as  surety  for  the  performance  of  this 
guaranty  the  contractor's  bond,  required  by  the  contract,  shall  remain 

in  full  force  until  the  expiration  of  the  period  of 

years  above  stipulated  in  this  section. 

The  importance  of  drafting  contracts  properly  cannot  well  be  over- 
estimated. An  incorrectly  drawn  agreement  is  almost  certain  to  involve 
serious  trouble  and  often  pecuniary  loss  to  an  innocent  party;  hence  it 
behooves  the  engineer  to  study  thoroughly  and  fundamentally  the  science 
or  art  of  contract  writing.  But  before  he  can  draft  a  contract,  he  must 
have  clearly  in  mind  a  full  and  well-defined  idea  of  all  the  conditions 
and  desiderata,  and  he  should  epitomize  these  systematically  before 
beginning  to  write.  It  is  advisable  to  keep  constantly  in  view  the 
possibility  that  each  party  to  the  contract  may  be  unscrupulous  and 
willing  to  take  every  possible  advantage  of  every  weakness  which  the 
contract  may  contain  and  which  will  tend  to  his  own  profit. 

The  essential  elements  of  any  contract,  according  to  Mr.  John  Cassan 
Wait,f  the  noted  authority,  are  as  follows: 

"1.  Two  parties  with  capacity   to   contract. 

"2.  A  lawful  consideration — a  something  in  exchange  for  its  legal 
equivalent,  a  quid  pro  quo. 

*  These  specifications  are  designed  to  secure  the  construction  of  the  pavement 
in  a  proper  manner,  the  city  assuming  responsibility  for  the  character  and  utility 
of  the  work.  The  guaranty  here  proposed  is  therefore  intended  to  cover  only  a  proper 
compliance  with  the  specifications,  for  which  the  contractor  may  properly  be  held 
responsible,  and  not  the  sufficiency  or  utility  of  the  work,  if  constructed  according 
to  the  specifications.  The  period  of  guaranty  should  therefore  be  short,  not  exceed- 
ing two  years. 

f  "Engineering  and  Architectural  Jurisprudence." 


482  THE  ART  OF  ROADMAKING 

"3.  A  lawful  subject-matter,  whether  it  be  a  promise,  an  act,  or  a 

material  object. 
"4.  Mutuality— a  mutual  assent,  a  mutual  understanding,  a  meeting 

of  the  minds  of  the  parties." 

Without  these  four  elements  no  contract  is  binding  in  law.  The 
essentials  of  a  well-drawn  contract  that  comes  within  the  province  of 
the  engineer,  however,  are  as  follows: 

1.  A  proper  and  customary  form. 

2.  A  full  and  correct  description  of  all  parties  to  the  agreement. 

3.  A  thorough  and  complete  preamble. 

4.  A  statement  of  when  and  under  what  conditions  the  contract  is 

to  become  operative. 

5.  The  limit,  if  any,  for  duration  of  contract. 

6.  An  exhaustive  statement  of  what  each  party  to  the  contract  binds 

himself,  his  executors,  his  administrators,  successors,  or  assigns, 
to  do  or  to  refrain  from  doing. 

7.  A   clearly   defined   enunciation   of   the   consideration   which   each 

party  is  to  receive;  this  is,  the  essential  raison  d'etre  of  the  instru- 
ment. 

8.  Forcasting    of    all    possible    eventualities    that    would    materially 

affect  the  agreement,  and  a  full  statement  of  everything  that 
is  to  be  done,  in  case  of  each  eventuality. 

9.  Penalties  for  failure  to  comply  with  the  various  terms  of  the  agree- 

ment. 

10.  Provision  for  possible  cancellation  of  contract. 

11.  Provision  for  settlement  of  all  business  relations  covered  by  the 

contract,  or  resulting  therefrom  in  case  of  cancellation,  taking 
into  account  all  possible  important  eventualities. 

12.  Mention  of  the  place  where  the  agreement  is  drawn  or  the  place 

where  it  is  to  be  put  in  force,  so  as  to  show  the  state  under  the 
laws  of  which  the  validity  of  the  contract  is  to  be  determined, 
should  suit  be  necessary  to  enforce  it. 

13.  Methods  of  payments,  if  any  are  to  be  made. 

14.  Provisions  for  extra  compensation,  and  the  limitations  connected 

therewith. 

15.  Provision  for  possible  changes  in  contract. 

16.  Provision  for  transfer  of  the  contract,  or  for  subletting. 

17.  Provision  for  settlement  of  disputes. 

18.  Provision  for  satisfactory  and  sufficient  bonds,  if  any  be  needed. 

19.  Provision  for  defense  of  law  suits,  if  such  provision  be  necessary. 

20.  Definition  of  names  used  in  contract,  such  as  "engineer,"  "com- 

pany," "contractor,"  or  "trustee." 

21.  Dating  of  contract. 

22.  Proper  signature  and  the  necessary  seals,  if  the  latter  be  required. 

23.  Witnesses  to  the  signatures,  or  execution  before  a  notary  public. 
As  illustrating  these  points,  the  following  example  of  a  good  typical 


SPECIFICATIONS  AND  CONTRACTS  483 

contract  may  be  reproduced.  This  is  the  standard  "Form  for  Contracts" 
of  Waddell  and  Harrington,  engineers,  of  Kansas  City,  Mo.,  for  appending 
to  construction  specifications  drawn  up  in  their  office. 

MEMORANDUM  OF  AGREEMENT,  made  and  signed  this day 

of 19 .  . ,  by  and  between  the 

the  party  of  the  first  part,  and  sometimes  termed  in  this  agreement  and 

in  the  specifications,  the  "company,"  and 

the  party  of  the  second  part,  and  sometimes  termed  in  this  agreement 
and  in  the  specifications  the  "contractor." 

WHEREAS, 

••• 

Now  THIS  AGREEMENT  WITNESSETH: 

First.  The  party  of  the  second  part,  for  and  in  consideration  of  cer- 
tain payments  to  be  made  to  it,  as  hereinafter  specified,  will 

all  in  accordance  with  the  plans  and  specifications  hereunto  annexed 
and  made  a  part  hereof,  and  will  fully  finish  and  complete  the  same 

by 

unless,  in  the  opinion  of  the  engineer,  the  party  of  the  second  part  be 
delayed  or  prevented  by  circumstances  that  are  absolutely  beyond  his 
control. 

Second.  The  party  of  the  second  part  shall  begin  the  work  of  con- 
struction as  soon  as  practicable  after  the  signing  of  the  contract,  and 
shall  push  the  same  to  completion  as  rapidly  as  possible,  and  within 
the  time  limit  or  limits  set  in  the  accompanying  specifications. 

Third.  All  important  dimensions  and  characteristics  of  the  struc- 
tures are  fully  described  in  the  accompanying  drawings  and  specifica- 
tions, which  form  a  part  of  this  contract. 

Fourth.  In  consideration  of  the  performance  by  the  party  of  the 
second  part  of  its  convenants  and  agreements,  as  hereinbefore  set  forth, 
the  party  of  the  first  part  hereby  covenants  and  agrees  to  pay  to  the 
party  of  the  second  part  as  follows: 


In  case  that  there  be  any  other  materials  furnished  by  the  contrac- 
tor that  are  not  included  in  this  list,  they  shall  be  paid  for  on  the  basis 
of  actual  cost  to  the  contractor  plus  ten  (10)  per  cent  for  his  profits. 

It  is  understood  that  no  payments,  either  partial  or  final,  are  to  be 
made  for  any  material  which  is  to  be  used  for  false  work  or  plant,  but 
only  for  such  material  as  is  left  permanently  in  the  finished  construction. 

Fifth.  The  schedule  prices  to  be  adopted  in  making  partial  pay- 
ments for  all  work  as  it  progresses  are  to  be  as  follows: 


Sixth.  All  material  paid  for  by  the  party  of  the  first  part  shall  be 
deemed  to  be  delivered  to,  and  to  have  become  the  property  of  the  said 
first  part,  but  the  party  of  the  second  part  hereby  agrees  to  store  it  and 
to  become  responsible  for  it  during  the  continuance  of  this  agreement. 
If  any  of  it  be  damaged,  destroyed,  or  lost  from  any  cause,  including, 


484  THE  ART  OF  ROADMAKING 

among  others,  floods,  washouts,  and  fires,  the  contractor  shall  repair 
or  replace  the  same  at  his  own  expense  to  the  satisfaction  of  the  engineer. 

Seventh.  In  case  the  party  of  the  first  part,  notwithstanding  the 
failure  of  the  party  of  the  second  part  to  complete  its  work  within  the 
time  specified,  shall  permit  the  said  second  party  to  proceed,  and  con- 
tinue and  complete  the  same,  as  if  such  time  had  not  elapsed,  such  per- 
mission shall  not  be  deemed  a  waiver  in  any  respect,  by  the  first  party, 
of  any  forfeiture  or  liability  for  damages  arising  from  such  non-com- 
pletion of  said  work  within  the  time  specified,  and  covered  by  the  "  Liqui- 
dated Damages"  clause  of  the  specifications;  but  such  liabilities  should 
be  continued  in  full  force  against  the  said  second  party,  as  if  such  per- 
mission had  not  been  granted. 

Eighth.  No  change  or  alteration  shall  be  made  in  the  terms  or  condi- 
'tions  of  this  agreement  without  the  consent  of  both  parties  hereto  in 
writing,  and  no  claim  shall  be  made  or  considered  for  any  extra  work 
unless  the  same  shall  be  authorized  and  directed  in  writing  by  the  engineer. 

Ninth.  In  the  event  of  any  delay  in  completing  the  work  embraced 
in  this  contract,  the  party  of  the  second  part  shall  be  entitled  to  no  extra 
compensation  on  account  of  such  delay,  as  it  is  hereby  assumed  that  in 
submitting  its  tender  it  took  its  chances  for  the  occurrence  of  such  delay. 
If,  however,  in  the  opinion  of  the  engineer,  the  contractor  be  delayed 
by  any  act  of  the  company  to  such  an  extent  as  to  cause  him  serious 
hardship,  such  as  temporary  cessation  of  the  work,  the  company  shall 
allow  the  contractor  whatever  compensation  for  such  delay  as  may  ap- 
pear to  the  engineer  to  be  just  and  equitable. 

Tenth.  The  party  of  the  second  part  hereby  agrees  that  it  will  not 
assign  or  sublet  the  work  covered  in  this  contract,  or  any  portion  of  it, 
without  the  written  consent  of  the  party  of  the  first  part,  but  will  keep 
the  same  within  its  control. 

Eleventh.  The  decision  of  the  engineer  shall  control  as  to  the  inter- 
pretation of  drawings  and  specifications  during  the  execution  of  the 
work  under  them;  but  if  either  party  shall  consider  itself  aggrieved  by 
any  decision,  it  may  require  the  dispute  to  be  finally  and  conclusively 
settled  by  the  decision  of  the  three  arbitrators,  the  first  to  be  appointed 
by  the  party  of  the  first  part,  the  second  by  the  party  of  the  second  part, 
and  the  third  by  the  two  arbitrators  thus  chosen.  In  case  that  the 
two  first  chosen  fail  to  agree  upon  a  third,  the  latter  shall  be  appointed 

by 

By  the  decision  of  these  three  arbitrators,  or  by  that  of  a  majority  of 
them,  both  parties  to  this  agreement  shall  be  finally  bound. 

Twelfth.  As,  according  to  the  terms  of  the  accompanying  specifica- 
tion, which  form  a  part  of  this  contract,  the  party  of  the  second  part  is 
to  indemnify  the  party  of  the  first  part  against  all  liability  or  damages 
on  account  of  accidents  occasioned  by  the  emission  or  negligence  of 
itself,  its  agents  or  its  workmen  during  the  continuance  of  this  agree- 
ment, and  against  all  claims  for  royalties  or  patents;  it  is  hereby  agreed 
that  the  party  of  the  second  part  shall  be  promptly  and  duly  notified  in 
writing  by  the  party  of  the  first  part  of  the  bringing  of  any  such  suit 
or  suits,  and  shall  be  given  the  privelege  of  assuming  the  sole  defence 
thereof.  The  party  of  the  second  part  is  to  pay  all  judgments  recovered 
by  reason  of  accidents  or  patents  in  any  suit  or  suits  against  the  party 
of  the  first  part,  including  all  legal  costs,  court  expenses,  and  other  like 
expenses. 

Thirteenth.  The  contractor  further  agrees  to  give  the  company  a 
surety-company  bond,  satisfactory  to  the  party  of  the  first  part  in  the 


OF 


SPECIFICATIONS  AND  CONTRACTS  485 

sum  of 

for  the  faithful  performance  of  this  contract  and  the  specifications,  and 
of  all  the  terms  and  conditions  therein  contained,  and  for  the  prompt 
payment  of  all  materials  and  labor  used  in  the  manufacture  and  con- 
struction of  the  structures,  and  to  protect  and  save  harmless  the  com- 
pany for  claims  on  patents  and  from  all  damages  to  persons  or  property, 
caused  by  the  negligence  or  claim  of  negligence  of  the  contractor,  his 
agents,  servants,  or  employees  in  doing  the  work,  or  in  connection  there- 
with, and  from  injury  to  or  loss  of  materials  paid  for  by  the  company 
either  partially  or  in  full  before  the  completion  and  acceptance  of  the 
construction  or  constructions. 

Fourteenth.  The  word  "Engineer"  as  used  in  this  contract  refers  to 

the  Consulting  Engineers  of  the 

or  their  duly  authorized  representative. 

IN  WITNESS  WHEREOF,  the  parties  to  this  agreement  have  hereunto 
set  their  hands  and  seals. 

Dated  the  day,  month,  and  year  first  herein  written. 

WITNESSED  BY 


APPENDIX  II 

PAVEMENT  GUARANTEES:   REASONS  FOR  SHORTENING 
OR   ABOLISHING   THEM* 

MANY  miles  of  pavements,  although  under  bonded  guaranty  for  good 
condition,  are  in  bad  order  on  many  streets  of  many  cities.  Municipal 
officials  and  taxpayers  are  rapidly  realizing  that  pavements,  when  first 
laid,  should  be  properly  constructed  under  the  responsible  and  direct 
supervision  of  the  city  engineering  department,  and  that  bonded  time 
guaranties  should  not  be  relied  upon,  but  be  abolished  or  at  least  reduced 
to  the  short  time  needed  to  enable  poor  construction  to  be  discovered 
and  replaced.  Who  would  think  of  having  a  city  hall,  water  works  or 
other  kinds  of  public  works  built  and  rely  upon  guaranties  that  these 
things  would  be  good  and  durable?  Private  works  are  not  conducted 
on  a  basis  of  guaranties,  but  upon  qua'ity. 

From  the  point  of  view  of  municipalities  and  property  owners,  the 
principal  objections  to  long-time  guaranties  are  as  follows: 

First.  Municipal  officials  are  naturally  often  careless  in  awarding 
contracts  when  accompanied  by  bonded  time  guaranties.  They  depend 
on  the  bond  rather  than  on  the  reliability  and  experience  of  the  contractor 
in  the  special  class  of  work  to  be  done.  They  often  investigate  the 
quality  of  the  bond  instead  of  the  quality  of  the  paving  material  offered. 
They  fail  to  have  complete  specifications  and  fail  to  depend  principally 
upon  efficient  supervision  by  the  city  engineer  of  the  materials  and  work 
during  construction.  It  is  often  stated  by  officials  of  boards  of  public 
works,  paving  committees,  etc.,  in  awarding  contracts  to  persons  or 
companies  whose  lack  of  experience  is  known  and  the  quality  of  their 
materials  unknown  or  whose  price  is  suspected  of  being  too  low  for  good 
work,  that  "  a  good  surety  bond  for  so  and  so  many  years  is  offered  and 
we  can  safely  rely  on  that."  There  are  hundreds  of  poor  pavements 
in  our  cities  built  under  "good  bonds";  but  a  "good  bond"  in  a  city 
file  is  not  a  good  pavement  on  a  city  street.  The  time  guaranty  bond 
is  a  very  unsatisfactory,  slow  and  uncertain  way  to  convert  a  poor  pave- 
ment into  a  good  one.  It  takes  a  pavement  from  the  control  of  the 
engineering  department  and  puts  it  for  a  long  period  as  a  burden  on  the 
legal  department  of  a  city. 

*  Abstracted  from  paper  on  "Pavement  Guarantees:  the  Use  and  Abuse,"  by  J. 
W.  Howard,  C.E.,  read  before  the  Board  of  Trade,  Newark,  N.  J.,  December,  1907. 

487 


488  THE  ART  OF  ROADMAKING 

Second.  Long-time  guaranties  have  very  seldom  proved  efficient  for 
getting  poor  pavements  made  good.  Nearly  every  city  has  many  pave- 
ments where  guaranties  have  not  been  complied  with.  There  are  but 
a  few  instances  of  recovery  by  a  city  of  damages  under  a  guaranty 
bond.  Because  law  is  a  slow  process,  the  pavements  meanwhile  become 
more  dilapidated.  I  speak  from  an  experience  of  some  years  during 
which,  aside  from  other  engineering  work  connected  with  pavements, 
I  have  examined  poor  pavements  and  my  reports  and  testimony  have 
helped  cities  collect  damages  from  defaulting  contractors  or  from  bonds- 
men. The  chief  engineer  of  pavements  of  Chicago  in  a  recent  paper 
showed  how  slow  and  unsatisfactory  the  legal  proceedings  are,  in  the 
cases  pending  in  Chicago  for  more  than  three  years,  to  compel  contractors 
or  bondsmen  to  put  their  pavements  in  order.  Many  contractors  and  all 
bonding  companies  have  attorneys  paid  by  the  year.  It  is  easier  and 
much  cheaper  for  them  to  prolong  litigation  than  to  repair  pavements. 

Third.  The  price  for  a  wrell-constructed  pavement,  when  time  guaranty 
bonds  are  required,  is  much  increased  by  reason  of  the  cost  of  surety 
company  bond  premiums,  the  cost  of  reserves  to  cover  unforseen  liabilities 
and  contingencies,  probable  lawsuits,  political  obstruction,  which  are 
factors  which  cannot  be  ignored  by  the  contractor,  and  which  are  included 
in  the  price  he  charges  for  the  pavement.  A  city  and  property-holder 
receives  practically  no  return  for  these  added  charges  for  time  guaranties. 

Fourth.  Incompetent,  inexperienced,  scheming  or  politically  affiliated 
contractors  sometimes  bid  low  prices  to  construct  pavements  without 
including  sufficient  to  cover  the  cost  of  proper  repairs  and  other  liabilities 
of  the  guaranty.  They  sometimes  deliberately  figure  on  the  basis  that 
if  the  pavement  should  fail  they  will  be  able,  in  some  way,  by  "friendship, 
political  influence  or  legal  process,  to  avoid  the  liability  of  the  guaranty. 
and  they  often  succeed.  Cities  are  too  likely  to  accept  such  bids.  Under 
the  unfortunate  laws  of  some  states,  cities  are  required  to  accept  such 
low,  "cheap"  bids,  although  offered  in  competition  with  the  bids  of 
experienced  and  conservative  contractors,  who  must  bid  higher  to 
furnish  durable  and,  in  the  end,  cheaper  pavements  for  the  city.  In 
states  requiring  its  cities  to  award  contracts  to  lowest  bidder,  it  is  easy  to 
abolish  time  guaranties  and  to  provide  complete  specifications,  thorough 
inspection  of  construction,  and  thus  quickly  eliminate  the  cheap-poor- 
work-bidder.  It  is  not  good  policy  nor  do  cities  wish  to  pay  for  anything 
less  than  cost  to  the  contractors.  They  are  willing  to  pay  a  fair  profit 
to  contractors  for  good  work. 

Fifth.  Time  guaranties  remove  from  the  municipal  engineer  or  officials 
in  direct  charge  of  the  work  the  right  to  fully  direct  important  details 
of  construction  in  accordance  with  their  best  judgment,  either  during  its 
first  construction  or  during  the  period  of  guaranty.  If  the  engineer 
exercises  his  prerogative  in  directing  how  any  of  the  details  are  to  be 
done,  the  contractor  and  the  bondsmen  are  thereby  often  found  to  be 
relieved  from  the  guaranty.  In  a  recent  decision  of  the  New  Orleans 


PAVEMENT  GUARANTIES  489 

District  Court,  Shea  v.  New  Orleans,  to  recover  money  for  work  alleged 
by  the  city  to  be  defective,  the  court  relieved  the  contractor  from  his 
guaranty,  because  the  work  was  done  in  accordance  with  directions  of  the 
engineer. 

Sixth.  A  city  should  not  lose  complete  control  of  its  streets  at  all 
times  by  having  the  pavements  on  the  surfaces  under  partial  control  of 
private  contractors,  as  they  practically  are  during  guaranty  periods. 
No  one  can  foretell  the  needed  uses  of  the  streets,  as  changes,  construction 
above,  below  or  adjacent  to  the  streets.  No  such  changes,  etc.,  can  be 
made  for  the  benefit  of  the  city  or  otherwise  without,  in  a  measure,  the 
city  or  property  holder  losing  the  asset  of  repairs  of  pavements  not  yet 
performed  during  the  balance  of  a  guaranty  subsequent  to  the  changes, 
etc.,  in  connection  with  the  street  which  are  needed  and  accomplished. 
A  city  cannot  properly  control  the  car-track  pavements  when  they  or 
even  the  adjacent  pavements  on  a  street  are  under  guaranties. 

Seventh.  It  is  often  illegal  to  require  long-time  guaranties  in  contracts 
for  construction  to  be  paid  for  by  assessment,  because  the  laws  require  the 
general  repair  to  pavements  due  to  general  use  of  pavements  shall  be  paid 
from  general  funds  of  the  city  and  forbid  such  repairs  to  be  assessed  as 
a  part  of  the  original  charge  or  otherwise  against  abutting  property. 
If  maintenance  guaranty  is  included  in  the  original  contract  price,  it 
generally  thereby  illegally  assesses  the  cost  of  maintenance  on  the 
abutting  property. 

Eighth.  A  city  whose  pavements  are  well  constructed  and  free  from 
time  guaranties  can  make  subsequent  repairs  due  to  wear  or  other  causes, 
either  by  using  its  own  employees  or  by  taking  advantage  of  new  com- 
petition which  constantly  arises.  It  can  avoid  being  tied  up  with 
possible  monopolies  or  being  kept  from  repairing  its  streets  for  long 
periods  by  having  annual  repair  contracts  and  paying  for  the  repairs 
each  time  they  are  made.  A  city  thus  avoids  the  heavy  bonding  and 
extra  indefinite  expenses  of  time  guaranties. 

Ninth.  Many  municipal  engineers  and  honest  experienced  city  officers 
are  of  the  opinion  that  it  is  not  for  the  interests  of  cities  to  require 
guaranties  beyond  such  period  as  will  bring  out  defects  due  to  neglect 
or  accident  and  that  such  defects  appear  within  one  or  two  years.  It 
seems  now  the  universal  opinion  that  a  contractor  shall  not  be  permitted 
to  guarantee  a  pavement  beyond  a  term  of  five  years,  because  not 
economical  nor  best  for  a  city.  It. is  a  well  known  fact  that  the  largest, 
most  conservative  and  responsible  paving  companies  charge  into  the 
cost  of  work  an  extra  cost  for  "reserve  for  maintenance  guaranty, "where 
time  guaranties  are  required  in  their  contracts. 

In  conclusion,  we  can  feel  sure  that  engineering  and  legal  experience 
shows  that  a  pavement  guaranteed  for  longer  than  five  years  is  neither 
economically  nor  legally  safe  or  best  for  city  or  taxpayer.  Two  years 
are  sufficient  to  demonstrate  the  quality  of  a  pavement  laid  under 
inspection  of  competent  men.  The  best  plan  for  city,  taxpayer  and  alJ 


490  THE  ART  OF  ROADMAKING 

concerned  is  a  guaranty  or  an  abeyance  of  final  acceptance  for  two 
years  from  the  first  of  June  first  following  the  completion  of  the  pavement, 
June  being  selected  because  experience  and  observation  demonstrate 
that  a  guaranty  should  terminate,  not  in  wet  or  cold  winter  weather, 
but  in  early  summer,  so  that  any  defects  will  be  fully  visible,  the  pavement 
easily  inspected,  the  repairs  properly  made  by  the  contractor  and  the 
city  receive  a  good  pavement. 


APPENDIX  III 

CONCERNING  THE  WEAR  OF  ROADS  BY  AUTOMOBILES 

SEVERAL  statements  have  already  been  given  in  Chapter  X  .to  demon- 
strate the  fact  that  high-speed  automobiles  are  injurious  to  the  ordinary 
road  surface,  but  in  these,  the  cause  of  the  damage  is  not  explained. 
As  an  example  of  this  damage  "Engineering  News"  recently  published 
an  abstract  from  a  German  contemporary  showing  the  result  of  a  con- 
centrated traffic  of  passenger  automobiles  upon  a  short  section  of  high- 
way in  Germany. 

Unusual  circumstances  subjected  this  short  stretch  of  road  to  very 
heavy  traffic  of  automobile  busses  for  a  period  of  five  months,  and  in 
that  period  some  interesting  studies  of  road  wear  were  made.  The  traffic 
was  much  heavier,  both  in  amount  and  in  loading,  than  normally  occurs 
even  on  heavily  traveled  main  highways,  and  the  results  represent  what 
might  be  called  an  accelerated'  test  of  road  destruction  by  motor-car 
traffic.  The  showing  made  is  rather  alarming,  but  in  reality  it  only 
puts  into  specific  figures  what  has  been  more  or  less  generally  recognized 
as  true. 

The  two  groups  of  cross-sections  shown  herewith  as  Figs.  1  and  2  give 
typical  illustrations  of  how  rapidly  the  traffic  cut  through  the  hard  sur- 
face of  the  highway.  The  circumstances  of  the  case  were  as  follows: 

A  railway  tunnel  between  the  towns  of  Mettlach  and  Ponten  caved 
in  on  Nov.  27,  1907;  this  interrupted  the  line  from  Trier  to  Saarbriicken 
and  necessitated  the  employment  of  auxiliary  means  of  transportation 
to  bridge  the  gap  for  passengers  and  baggage.  An  average  of  10  passen- 
ger-trains each  way  per  day  had  to  be  taken  care  of. 

For  a  fortnight  local  vehicles,  such  as  cabs,  farm  wagons,  etc.,  were 
employed.  On  Dec.  6,  two  closed  motor-cars  holding  12  to  15  passengers 
each  were  obtained.  A  week  later  ten  large  motor-busses  belonging 
to  the  Grosse  Berliner  Motor-Omnibus  Co.,  were  put  into  service  on 
the  portage  and  the  two  smaller  busses  were  dismissed.  These  ten  busses 
were  in  service  till  early  in  February,  when  four  of  them  burned,  after 
which  the  remaining  six  handled  the  service. 

The  tunnel  was  restored  ready  for  traffic  by  May  1,  1908,  making  the 
period  of  road  portage  practically  five  months.  During  this  time  the 
motor-busses  averaged  80  trips  between  Ponten  and  Mettlach,  though 
m  the  Christmas  weeks  the  number  of  trips  was  increased  to  as  high  as 
140  per  day. 

491 


492 


THE  ART  OF  ROADMAKING 


FIG.  1. — A  Typical  Cross- section  of  the  North  Slope. 


,^.— 


J  J 


0,0 

Febr.  15, 1 


Z^5S 


Febr.E4.l908. 


33  M          I  pi  i I  J  ' 

a   ai  a  si   a  si    si     ?i 


FIG.  2. — A  Cross-section  on  the  Upland. 


THE  WEAR  OF  ROADS  BY  AUTOMOBILES 


493 


The  stretch  of  road  in  question,  excluding  the  terminal  portions  which 
lay  in  paved  streets,  is  slightly  under  two  miles  long.  A  short  stretch 
near  the  middle  is  level,  lying  on  the  ridge  through  which  the  railroad 
tunnels,  while  the  rest  is  steeply  sloped  down  toward  the  two  ends. 
The  northerly  slope  averages  6.9  per  cent  grade,  the  southerly  slope  8 
per  cent.  The  road  had  a  broken-stone  pavement,  generally  a  kind  of 
Telford,  i.e.,  there  was  a  base  course  of  shingle  or  cobbles.  The  upper 
course  consisted  of  quartzite,  stated  to  be  very  suitable  for  road  purposes. 


FIG.  3.— View  of  the  Rutted  Road  Surface  in  Winter. 


The  age  of  the  road  surfacing  varied,  but  the  important  feature  is  that 
the  older  parts  had  been  kept  in  careful  repair,  and  the  entire  two-mile 
length  was  in  first-class  condition. 

Perceptible  wear  began  when  the  large  motor-busses  came  into  ser- 
vice. A  picking-up  action  was  noticed  in  the  tire  tracks,  and  in  a  few 
days  the  road  was  covered  with  fragments  of  stone  torn  out  of  the  sur- 
facing. Further,  although  the  gage  of  the  rear  wheels  was  larger  than 


494  THE  ART  OF  ROADMAKING 

that  of  the  front  wheels,  the  concentration  of  wear  from  tracking  soon 
produced  the  results  shown  in  the  sketches. 

These  large  busses  are  described  as  follows:  Weight,  empty,  13,000 
Ibs.,  of  which  nearly  9,500  Ibs.  was  on  the  rear  axle;  capacity,  25  pass- 
engers; weight  loaded,  about  17,000  Ibs.;  tires,  solid  rubber,  width 
4  ins.  front,  8|  ins.  rear;  gauge,  5.9  ft.  front,  6.6  ft.  rear;  speed,  6  to  15 
miles  per  hr. 

The  rutting  of  the  road  once  started,  it  developed  in  a  short  time 
so  far  as  to  form  grooves  up  to  6  ins.  deep  by  12  ins.  wide,  and  ridges 
formed  alongside  the  ruts  from  the  displaced  material.  The  ruts  were 
not  clean  but  contained  much  loose  material,  which  the  following  wheels 
either  pushed  aside  or  crushed. 

Repair  work  was  started  as  soon  as  the  destructive  actions  were  no- 
ticed, and  was  continued  to  the  end  of  the  period.  Coarse  broken  stone 
was  placed  in  the  ruts  and  pressed  down  with  a  steam  roller,  whereupon 
a  binding  course  of  small  stuff  such  as  cinders  and  coarse  sand  was  sim- 
ilarly applied.  This  could  be  done  only  when  the  road  was  not  frozen. 

Two  weeks  often  sufficed  to  destroy  the  repair  work  completely. 
During  the  last  three  months  it  was  a  constant  struggle  to  keep  the  road 
in  passable  condition.  If  heavy  continued  rains  had  occurred  in  March 
or  April  it  would  have  been  impossible  to  maintain  the  traffic. 

The  wear  and  grooving  was  worse  in  December.  Freezing  weather 
in  January  and  the  first  part  of  February  held  matters  stationary  and 
preserved  the  road,  though  in  badly  rutted  condition.  Thereafter  the 
southerly  slope  thawed  first,  and  repair  work  was  concentrated  on  it, 
the  northerly  slope  being  taken  up  later. 

The  five-month's  maintenance  cost  about  $4,000,  or  over  $2,000  per 
mile.  About  1,250  cu.  yds.  broken  stone  and  an  undetermined  amount 
of  sand  and  cinders  were  used.  Mr.  M.  Gorz,  who  reports  the  details, 
says  that  but  for  good  weather,  a  convenient  supply  of  materials  and 
the  availability  of  labor  from  the  railway  department  it  would  not  have 
been  possible  to  keep  up  the  road.  These  favorable  factors,  we  conclude, 
also  operated  to  reduce  the  cost. 

The  influence  of  the  heavy  weight  concentrations  upon  the  destruc- 
tion of  the  road  was  evident  in  one  of  the  paved  streets  at  one  end  of  the 
route.  A  street  newly  paved  with  stone  block,  but  apparently  without 
concrete  base,  was  used  temporarily  to  detour  around  the  main  street. 
But  in  a  few  days  the  surface  was  deeply  grooved,  the  wheels  crushing 
the  stone  blocks  down  into  the  soil,  and  the  busses  had  to  use  another 
street. 

This  is  a  most  graphic  example  of  the  serious  damage  done  by  auto- 
mobile tires  to  road  surface.  Yet,  around  the  suburbs  of  any  of  the 
larger  cities  we  can  find  almost  equally  serious  examples  of  wear  at 
any  place  where  automobile  traffic  is  concentrated,  particularly  where 
high  speeds  are  possible  and  around  curves. 

Commmenting  on  this,  "Engineering  News"  says: 


THE  WEAR  OF  ROADS  BY  AUTOMOBILES 


495 


"A  dozen  years  or  so  ago,  prophecies  were  common  that  a  golden  age 
for  roads  and  streets  would  come  when  horses  should  be  displaced  by 
self-propelled  vehicles.  The  horse,  it  was  claimed,  was  the  chief  instru- 
ment in  the  wear  of  our  roads  and  highways,  by  digging  up  the  surface 
with  the  calks  on  his  shoes.  The  iron  tire  of  horse-drawn  vehicles,  too, 
was  referred  to  as  a  crushing  mill  which  was  continually  reducing  to 
powder  the  material  of  the  roadway  surface.  'Only  give  us  vehicles 
without  horses,  with  the  wheel  treads  fitted  with  rubber  tires/  it  was 
said,  'and  the  wear  on  the  roads  will  be  reduced  practically  to  nothing.' 

"  It  is  interesting  to  reflect  on  these  ideas  so  commonly  held  a  dozen 
years  ago,  and  to  compare  them  with  the  actual  experience  with  the 
automobiles  of  the  present  day. 

"The  question  may  well  be  asked:  why  should  the  theory  of  a  dozen 
years  ago  be  so  far  apart  from  the  experience  of  to-day?  Why  does  the 
automobile  tire,  which  was  expected  to  produce  no  wear  at  all  upon 
roads,  actually  wear  them  so  terrifically? 

"It  is  worth  while  studying  this  question,  because  when  the  answer 
is  found  it  is  an  excellent  illustration  of  the  fact  that  really  theory  and 
practice  are  not  in  conflict,  as  might  at  first  sight  appear.  The  only 
trouble  with  the  theory  of  a  dozen  years  ago  was  that  it  did  not  take 
all  the  facts  into  consideration.  Hindsight  is  proverbially  better  than 
foresight;  and  now  that  we  know  how  badly  the  automobile  wears  our 
road  surfaces,  it  is  not  difficult  to  see  why  this  wear  occurs. 

"  In  the  first  place,  one  important  factor  is  the  driving  or  propelling 
action  of  the  automobile  wheels.  With  horse-drawn  vehicles,  of  course, 
there  is  no  driving  action  by  the  wheels,  and  they  exert  only  a  downward 
pressure  or  lateral  pressure  on  the  road.  The  rear  tires  of  an  automo- 
bile, however,  exert  not  only  a  downward  pressure  upon  the  road  sur- 
face, but  a  powerful  tangential  push  to  the  rear.  The  average  power 


Direction 
of  Motion 


FIG.  4. 


D         C 
FIG.  5. 


of  the  automobiles  in  common  use  to-day  is  probably  from  15  to  40  H.P., 
and  the  speeds,  outside  of  city  streets,  will  average  not  less  than  15  to 
30  miles  per  hour.  If  we  consider  the  elements  of  a  rubber  wheel-rim  in 
contact  with  the  surface  of  the  ground,  Fig.  4,  it  may  be  easily  seen 
that  the  point  A,  which  has  just  come  into  contact  with  the  road  surface, 
exerts  no  tangential  action  upon  the  road.  As  the  wheel  moves  for- 


496  THE  ART  OF  ROADMAKING 

ward  from  A  to  B,  however,  this  tangential  push  of  the  surface  of  the 
rubber  tire  against  the  road  rapidly  increases  from  zero  at  A  to  a  max- 
imum at  B,  and  as  the  tire  lifts  from  the  road  at  B  and  the  pressure 
is  released,  the  tendency  is  to  push  backward  the  material  of  the  road 
just  beneath  it. 

"There  is  another  reason  why  the  automobile  tire  rapidly  digs  a  rut 
for  itself  on  any  road  where  automobiles  follow  each  other  and  keep 
nearly  in  the  same  track.  The  vehicle  fitted  with  iron  tires  has  a  flat 
tread;  the  rubber  tire,  either  pneumatic  or  solid,  has  a  tread  which  is 
more  or  less  rounded.  Suppose,  in  a  given  automobile  wheel,  Fig.  5, 
the  diameter  at  the  center  of  the  tread  at  C  is  30  ins. ;  then  the  diameter 
toward  the  sides  of  the  tread  at  D  may  be  |-in.  or  ^-in.  less,  depending 
upon  the  pressure  to  which  the  tire  is  pumped,  the  contour  of  the  tire 
cross-section,  the  weight  carried  by  the  automobile,  etc.  If  we  take 
only  | -in.  difference  in  diameter  at  the  points  C  and  D,  we  have  a  dif- 
ference in  circumference  between  the  central  part  of  the  tread  and  the 
sides  of  the  tread  of  about  f-in.  That  means  that  at  every  revolution 
of  the  wheel,  either  the  center  of  the  tread  must  slip  f-in.  forward,  or 
the  sides  of  the  tread  must  slip  f-in.  backward;  that  is  to  say,  there  must 
be,  theoretically  and  actually,  this  difference  in  the  relative  movement 
of  the  center  and  the  sides  of  the  tread  upon  the  roadway.  Actually, 
of  course,  this  slip  is  going  on  all  the  time  in  the  movement  of  a  rounded 
tire.  There  is  some  point  between  the  center  and  the  side  where  no 
slip  occurs,  and  toward  the  center  or  toward  the  side  there  is  all  the 
time  a  slight  slip  forward,  or  backward.  As  a  result  of  this  action,  the 
round-tired  vehicle  has  more  rolling  friction  than  a  vehicle  with  flat 
tires.  Of  course,  on  an  ordinary  roadway  such  as  a  brick  pavement  or 
a  smooth  macadam,  the  pneumatic  tire,  notwithstanding  its  rounded 
surface,  may  move  with  little  friction  because  the  small  stones  and  sim- 
ilar obstructions  which  would  be  crushed  by  the  iron  tire  will  simply 
indent  the  pneumatic  tire.  On  an  ordinary  dirt  road,  however,  the 
rounded  rubber  tire  has  more  resistance  to  traction  than  a  flat  iron  tire. 

"It  is  probable  that  the  wear  of  the  rubber  tire  on  the  roadway  is 
more  rapid  as  a  rut  begins  to  form  and  the  width  of  contact  of  the  tire 
with  the  road  is  thus  increased.  In  the  rut  the  sides  of  the  tread — 
points  where  the  tire  diameter  is  an  inch  or  even  two  inches  less  than 
at  the  center — may  be  in  contact  with  the  road.  If  the  center  of  the 
tire  moves  in  the  rut  without  slip,  the  sides  of  the  tire  where  the  diameter 
is  2  ins.  less  must  slip  6  ins.  forward  against  the  sides  of  the  rut  at  every 
revolution.  Thus  the  retarding  action  of  the  sides  of  the  rut  tends  to 
increase  the  tangential  force  of  the  center  of  the  tire  upon  the  roadway 
and  to  dig  the  rut  deeper. 

"We  are  aware  that  the  tearing  out  of  the  macadam  surface  by  the 
pneumatic  tires  of  an  automobile  has  been  frequently  ascribed  to  the 
'suction'  of  the  tire  upon  the  roadway.  We  do  not  see,  however,  in  view 
of  the  foregoing  explanation,  that  any  'suction'  hypothesis  is  needed 


THE  WEAR  OF  ROADS  BY  AUTOMOBILES  497 

to  explain  the  disintegration  of  a  macadam  road  surface  by  automobiles. 
Of  course  there  is  a  wind  current — an  upward  and  forward  suction — 
produced  at  the  rear  of  the  tires  of  a  fast  running  automobile,  and  this 
wind  current  raises  the  fine  dust  loosened  by  the  tire  from  the  surface 
and  sends  it  high  in  the  air.  Observation  of  this  easily  seen  phenom- 
enon has  given  rise  to  the  common  idea  that  the  suction  of  the  wheel 
on  the  road  surface  is  what  loosens  the  stone.  Some  such  suction  there 
doubtless  is  and  it  may  possibly  be  a  slight  contributing  cause  of  destruc- 
tion; but  any  force  exerted  in  this  way  must  be  very  small  compared 
with  the  terrific  backward  push  of  the  rubber  tire  treads. 

"  In  the  light  of  the  above  discussion  it  is  evident  that  little  can  be 
hoped  for  in  the  way  of  help  for  the  roads  through  changes  in  automobile 
construction.  Flat  steel  tires  in  place  of  pneumatic  tires  might  possibly 
reduce  the  wear  upon  the  roads;  but  the  success  of  the  automobile  is 
dependent  on  noiseless  and  easy-riding  rubber  tires.  Further,  we  are 
only  at  the  threshold  of  our  troubles  with  highways  due  to  automobile 
wear.  For  two  years  automobile  factories  have  been  working  over- 
time, and  it  is  said  that  200,000  automobiles  are  to  be  built  next  year. 
The  burden  on  taxpayers  to  build  and  maintain  roads  to  carry  automo- 
bile traffic  promises  to  become  so  great  that  a  road  repair  tax  may  have 
to  be  laid  on  the  vehicles  themselves." 


APPENDIX  IV 

STATISTICS   OF   PUBLIC    ROADS   OF   THE   UNITED    STATES* 

IN  the  year  1904  there  were  2,151,570  miles  of  public  roads  in  the 
United  States.  This  does  not  include  roads  in  Indian  Territory, 
Alaska,  and  the  island  possessions,  as  Indian  Territory  and  Alaska  were 
not  organized,  by  counties  in  1904,  and  it  was  impossible  to  secure  com- 
plete information  from  Porto  Rico,  Hawaii,  the  Philippines  and  Guam. 
Neither  does  this  total  mileage  of  roads  include  streets  or  boulevards  in 
incorporated  cities  and  villages.  Of  this  mileage  108,232.9  miles  were 
surfaced  with  gravel,  38,621.7  miles  with  stone,  and  6,809.7  miles  with 
special  materials,  such  as  shells,  sand-clay,  oil,  and  brick,  making  in  all 
153,664.3  miles  of  improved  road,  or  7.14  per  cent  of  all  the  roads  in  this 
country. 

A  comparison  of  the  total  road  mileage  writh  the  area  of  all  the  states 
and  territories,  shows  that  there  was  0.73  of  a  mile  of  road  per  square  mile 
of  territory,  and  a  similar  comparison  with  population  shows  that  there 
was  one  mile  of  road  to  every  35  inhabitants,  and  one  mile  of  improved 
road  to  every  492  inhabitants. 

The  majority  of  all  the  roads  in  this  country  were  originally  laid  out 
along  the  boundary  lines  of  farms,  with  little  regard  for  drainage,  topog- 
raphy and  alignment.  In  the  eastern  states  the  boundary  lines  of  farms 
were  very  irregular,  and  consequently  many  of  the  roads  are  crooked 
and  badly  located  with  reference  to  grades.  In  the  middle  wrest,  where 
the  land  was  laid  out  by  the  Government,  the  roads  follow  the  section 
lines,  and  in  thickly  settled  communities  the  quarter-section  lines.  In 
compiling  these  figures  the  aim  was  to  include  only  the  mileage  of  roads 
actually  open  and  in  use;  but  in  reports  from  some  of  the  counties  in  the 
middle  west  may  have  included  a  greater  or  less  mileage  of  section  lines, 
which  have  been  set  apart  by  law  as  public  roads,  but  which  have  not 
been  opened  up  or  used  for  this  purpose. 

Only  four  states  have  more  than  100,000  miles  of  roads.  Texas  stands 
first,-  with  121,409  miles;  Missouri  second,  with  108,133;  Iowa  third, 
with  102,448;  and  Kansas  fourth,  with  101,196.  The  District  of  Colum- 
bia has  only  191  miles  of  roads,  Rhode  Island  has  2,361  miles,  which  is 

*  Abstracted  and  condensed  from  "  Public  Road  Mileage,  Revenues  and  Expenditures 
in  the  United  States,  in  1904"— Public  Document,  Bulletin  No.  32,  U.  S.  Dept.  of 
Agriculture,  in  which  the  road  statistics  for  all  the  States  and  Territories  are  given. 

499 


500  THE  ART  OF   ROADMAKING 

the  smallest  mileage  of  any  state.     Delaware  has  only  3,000,  and  Arizona 
only  5,987  miles. 

By  comparing  the  road  mileage  with  the  areas  in  square  miles,  the 
District  of  Columbia  is  found  to  stand  first,  with  3.18  miles  of  road  per 
square  mile  of  area,  while  Connecticut  is  highest  among  the  states  with 
2.90  miles.  Rhode  Island  has  2.24  miles,  and  Pennsylvania  2.21  miles 
per  square  mile  of  area.  Arizona  has  only  0.05  of  a  mile,  the  smallest 
mileage  per  square  mile;  Utah  has  0.08  and  Wyoming  0.10  of  a  mile  per 
square  mile. 

A  comparison  of  the  mileage  of  roads  with  population  shows  that  the 
District  of  Columbia,  which  embraces  a  land  area  of  60  square  miles  and 
which  includes  the  city  of  Washington,  has  the  largest  population  per 
mile  of  public  road,  i.e.,  1.459.  Rhode  Island  has  the  largest  population 
per  mile  of  any  state,  i.e.,  181  inhabitants;  Massachusetts  has  164,  New 
Jersey  127,  and  Connecticut,  64.  On  the  other  hand,  Nevada  has  only 
3  persons  per  mile  of  public  road;  North  Dakota  has  5  persons;  South 
Dakota  has  7;  Wyoming  8;  Idaho  and  Oklahoma,  9  each;  and  Montana, 
10. 

Assuming  the  average  width  of  the  rights  of  way  of  country  roads  in  the 
United  States  to  be  40  feet,  the  area  of  such  rights  of  way  in  1904  amounted 
to  10,431,727  acres.  Estimating  the  value  of  this  land  on  a  basis  of  the 
valuation  of  farm  lands  in  each  state,  the  approximate  value  of  the  rights 
of  way  of  all  the  public  roads  would  be  $341,899,306.  A  much  higher 
valuation  would  be  amply  justified  by  the  fact  that  in  sections  where  the 
mileage  of  roads  is  greatest  the  land  is  considerably  above  the  average  In 
value.  A  much  higher  estimated  value  would  also  result  from  assuming 
that  the  rights  of  way  of  roads  are  as  valuable  as  the  contiguous  farm 
lands,  which  are  always  worth  considerably  more  than  the  general 
average.  The  value  of  the  rights  of  way,  however,  constitutes  a  very 
small  part  of  the  value  of  the  roads  when  we  take  into  consideration  the 
amount  that  is  expended  in  material  and  labor  in  improving  and  main- 
taining them.  The  approximate  value  of  rights  of  way  is  therefore  given 
merely  as  an  item  of  some  importance  in  any  calculations  which  may  be 
made  as  to  value. 

It  was  generally  believed  at  the  time  when  railroad  building  was 
first  undertaken  in  this  country  that  the  railroad  would  supplant  the 
wagon  road,  and  this  line  of  reasoning  account  in  a  large  measure  for  the 
neglect  of  the  common  roads  from  about  1835  until  about  1890.  It  is  now 
clearly  demonstrated  that  in  spite  of  the  fact  that  the  United  States  leads 
the  world  in  railroad  building,  having  a  total  of  213,904  miles  in  1904, 
the  necessity  for  the  improvement  of  our  common  roads  is  impressing 
itself  upon  the  people  more  now  than  at  any  time  in  the  history  of  the 
country.  Our  mileage  of  public  roads  is  greater  now  than  it  has  ever 
been,  and  the  extension  of  railroad  and  trolley  lines  has  induced  such  an 
amazing  development  of  the  country's  resources  as  to  bring  about  a 
remarkable  increase  in  traffic  over  the  common  roads.  The  heads  of 


PUBLIC  ROADS  OF  THE  UNITED  STATES  501 

the  great  railroad  systems  are  now  seriously  directing  their  efforts  toward 
securing  the  improvement  of  the  common  roads,  which  they  recognize 
as  feeders  to  their  railroad  lines.  In  this  connection  it  is  interesting  to 
observe  that  for  every  mile  of  railroad  we  have  about  ten  miles  of  wagon 
roads. 

MILEAGE  OF  IMPROVED  ROADS.  Of  the  153,662  miles  of  improved 
roads  in  the  United  States,  Indiana  has  the  largest  mileage — that  is, 
23,877  miles.  Ohio  occupies  the  second  place,  with  23,460  miles;  Wis- 
consin is  third,  with  10,633  miles;  Kentucky  fourth,  with  9,486  miles; 
California  fifth,  with  8,803  miles.  Illinois,  Massachusetts,  and  Michigan 
have  over  7,000  miles  each;  Minnesota  over  6,000  miles;  New  York  over 
5,000  miles;  Tennessee  over  4,000  miles;  Connecticut,  Maine,  Missouri, 
New  Jersey,  Oregon,  Pennsylvania,  and  Texas  over  2,000  miles  each; 
and  Alabama,  Georgia,  Iowa,  Maryland,  New  Hampshire,  North  Carolina, 
Rhode  Island,  South  Carolina,  Vermont,  Virginia  and  Washington  over 
1,000  miles  each. 

In  about  two-thirds  of  the  states  gravel  has  been  the  principal 
surfacing  material  used  in  improving  the  roads.  The  largest  mileage  of 
gravel  roads  was  found  in  Indiana,  Ohio,  Wisconsin,  Massachusetts, 
Michigan,  Minnesota,  Illinois  and  California.  In  eight  states  the  mileage 
of  macadam  roads  exceeds  that  of  gravel,  and  in  a  few  others  it  is  nearly 
equal.  Kentucky  has  the  largest  mileage  of  road  surfaced  with  stone — 
over  8,000  miles — and  Ohio  is  second,  with  a  little  over  7,000.  Other 
states  with  large  mileage  of  this  class  are  Indiana,  New  York,  Pennsyl- 
vania, Texas,  and  New  Jersey.  About  one-third  of  the  improved  roads 
of  California  were  treated  with  oil ;  and  almost  all  of  the  improved  roads 
in  South  Carolina  were  surfaced  with  mixtures  of  sand  and  clay. 

PERCENTAGE  OF  ROADS  IMPROVED.  The  district  of  Columbia  occupies 
the  first  place  in  its  percentage  of  roads  improved,  having  65.58  per  cent 
improved.  Massachusetts  has  45.89  per  cent,  the  highest  percentage 
of  any  state.  Rhode  Island  comes  next,  with  43.26  per  cent;  then  follow 
Indiana,  with  34.94;  Ohio,  with  33.78;  California,  with  18.87 ;  Connecticut 
with  16.75;  Wisconsin,  with  16.72;  Kentucky,  with  16.60;  New  Jersey, 
with  16.32;  Michigan,  with  10.13;  Maine  and  Maryland,  each  with  a 
little  over  9;  Illinois,  New  Hampshire,  Tennessee  and  Utah,  each  with 
over  8;  and  Minnesota,  New  York  and  Oregon,  each  with  over  7  per  cent. 
All  of  the  states  and  territories  except  Oklahoma  report  some  improved 
roads.  Eleven  of  the  states,  however,  report  less  than  11  per  cent 
improved. 

A  comparison  of  the  percentage  of  roads  improved  with  the  population 
per  mile  of  road  shows  that  in  most  cases  the  states  which  have  the 
highest  percentage  of  improved  roads  have  the  largest  population  per 
mile  of  road,  and  vice  versa.  While  it  cannot  be  claimed  for  improved 
roads  that  they  invariably  lead  to  an  increase  in  population,  good  roads 
are  certainly  a  powerful  factor  in  encouraging  immigration,  especially 
in  sparsely  settled  regions. 


502  THE  ART   OF    ROADMAKING 

The  percentage  of  improved  roads  in  any  community  or  state  depends 
upon  a  variety  of  causes,  the  most  important  of  which  may  be  summed 
up  as  follows: 

(1)  Availability  of  suitable  road-building  material. 

(2)  Wealth  of  the  state  in  agriculture,  manufactories,  transportation, 
etc. 

(3)  Requirements  of  traffic. 

Prosperity  promotes  a  desire  for  the  advantages  and  benefits  to  be 
derived  from  the  improvement  of  the  roads;  but  whether  a  community 
is  rich  in  agriculture  or  otherwise,  if  it  has  to  depend  on  materials 
imported  from  distant  places,  progress  in  the  improvement  of  the  roads 
will  be  much  slower  than  if  local  materials  are  abundant.  To  illustrate 
this  point:  Mississippi  expended  in  money  and  labor  about  the  same 
amount  on  roads  in  1904  as  Tennessee;  yet  Mississippi,  which  is  very 
poor  in  road  surfacing  materials,  has  only  .38  per  cent  of  the  roads 
improved,  while  in  Tennessee,  which  is  well  supplied  with  such  materials, 
8.74  per  cent  of  the  roads  are  improved. 

There  are  several  other  reasons  why  the  percentage  of  improved  roads 
is  higher  in  some  of  the  states  than  in  others.  The  high  percentage 
of  improved  roads  in  Massachusetts,  Rhode  Island,  Connecticut,  and 
New  Jersey  is  due  principally  to  the  facts  that  suitable  road-building 
materials  abound,  that  these  states  are  densely  populated,  and  that 
many  of  the  roads  have  been  built  through  the  aid  of  the  states  and  under 
the  direction  of  competent  state  authorities.  Indiana  and  Ohio  have  an 
unusually  high  percentage  of  improved  roads,  because  these  states  are 
abundantly  supplied  with  good  road-building  stone  and  gravel  and 
because  the  social  and  economic  conditions  were  favorable  to  the  making 
of  public  improvements. 

A  comparison  of  the  percentage  of  roads  improved  with  the  acreage 
values  of  farm  lands  in  the  United  States  shows  that  the  average  percent- 
age of  the  improved  roads  in  all  states  where  the  land  is  worth  less  than 
$20  per  acre  is  1.9  per  cent,  whereas  in  the  states  showing  an  acreage 
value  of  more  than  $20,  improved  roads  constitute  an  average  of  9  per 
cent  of  the  total  mileage. 

Expressed  inversely,  the  states  showing  a  high  percentage  of  improved 
roads  have  on  the  average  relatively  high  acreage  values,  while  those 
showing  a  low  percentage  have  low  acreage  values. 

In  Mississippi,  for  instance,  the  farm  lands  are  worth  on  the  average 
only  $15.94  per  acre,  and  in  1904  the  percentage  of  improved  roads  was 
0.38  of  1  per  cent,  while  in  Indiana  we  find  that  the  farm  lands  are  valued 
at  $54.96  per  acre,  and  the  improved  roads  in  1904  constituted  35  per 
cent  of  the  total  mileage.  In  Arkansas  the  farms  are  worth  $16.67  per 
acre,  while  the  percentage  of  improved  roads  in  1904  was  only  0.7  per 
cent.  The  corresponding  figures  for  Ohio  are:  acreage  value  of  farms, 
$57.43,  and  percentage  of  improved  roads,  33.7  per  cent. 

While  there  are  many  factors,  such  as  quality  of  the  soil,  the  proximity 


PUBLIC  ROADS  OF  THE  UNITED  STATES  503 

of  farms  to  markets,  and  the  relative  population  and  wealth,  which  affect 
the  value  of  the  land,  the  figures  given  above  indicate  that  the  improve- 
ment of  the  roads  constitute  a  most  important  factor  in  the  enhancement 
of  farm  values.  Records  are  on  file  to  show  that  farm  lands  have  been 
known  to  advance  in  value  from  50  to  500  per  cent  on  account  of  the 
improvement  of  the  roads  connecting  them  with  market  towns. 

Of  the  108,232.9  miles  of  gravel  road  in  the  United  States,  Indiana 
has  20,582  miles,  and  leads  all  other  states  in  this  class  of  roads;  Ohio 
comes  second,  with  16,159  miles,  Wisconsin  has  9,899.8  miles,  and  Illinois 
6,800  miles.  The  large  mileage  of  gravel  roads  in  these  states  is  due  in 
part  to  the  fact  that  they  are  abundantly  supplied  with  gravel  suitable 
for  road  building,  most  of  this  being  of  glacial  origin. 

Of  the  38,622  miles  of  road  surfaced  with  stone,  Kentucky  leads  with 
8,078  miles;  Ohio  stands  next  with  7,160.5  miles;  Indiana  has  3,295 
miles ;  New  York  and  Pennsylvania  have  over  2,000  miles  each,  and  Illinois, 
Massachusetts,  New  Jersey,  Tennessee,  and  Texas  have  each  over  1,000 
miles. 

One  of  the  largest  limestone  belts  in  the  United  States  extends  through 
Kentucky,  Ohio,  and  Indiana,  and  most  of  the  stone  roads  in  these  states 
are  built  of  this  material.  Furthermore,  Kentucky  has  been  building  stone 
roads  since  1829,  most  of  them  being  constructed  under  the  turnpike  or 
toll  system.  This  state  also  aided  in  this  work  for  several  years,  and 
at  the  close  of  1837  had  invested  $2,509,473  in  turnpike  roads.  At  that 
time  609  miles  of  first-class  stone  roads  had  either  been  constructed  or 
were  under  construction. 

In  1829  the  old  National  or  Cumberland  road  was  completed  in  parts 
of  Ohio,  this  being  apparently  the  first  stone  road  built  in  the  state. 
From  1840  to  the  present  time  the  building  of  stone  roads  has  continued 
steadily.  Some  were  built  under  the  toll  system,  some  under  the  one 
and  two  mile  assessment  plans,  and  others  from  bond  issues. 

The  first  macadamized  road  in  Indiana  was  built  in  1839.  It  was  the 
first  and  only  road  built  by  the  state,  and  extended  from  New  Albany 
to  Paoli.  From  1850  to  1890  many  stone  roads  were  built  in  that  state 
under  the  turnpike  or  toll  system,  and  in  1885  the  construction  of  free 
gravel  and  stone  roads  began — that  is,  roads  on  which  travelers  were  not 
required  to  pay  toll.  From  1893  to  the  present  time  many  miles  of 
stone  roads  have  been  built  by  the  various  townships  from  funds  received 
from  bond  issues. 

Of  the  6,807  miles  of  road  in  the  United  States  surfaced  with  special 
materials,  California  has  2,541  miles  surfaced  with  oil;  South  Carolina 
has  1,630  miles,  nearly  all  surfaced  with  sand-clay  mixtures;  Florida 
and  Georgia  has  each  over  500  miles  mostly  surfaced  with  sand-clay 
mixtures;  North  Carolina  has  438  miles  surfaced  with  sand-clay;  Mary- 
land has  250  miles  of  roads  surfaced  with  shells,  and  Ohio  has  140.7  miles, 
most  of  which  is  surfaced  with  brick. 

Oyster  shells  from  Chesapeake  Bay  have  been  extensively  used  for  a 


504  THE  ART  OF  ROADMAKING 

number  of  years  in  building  shell  roads  in  Maryland  and  Virginia.  A 
considerable  mileage  of  shell  roads  is  also  reported  for  most  of  the  Atlantic 
and  Gulf  Coast  States.  Ohio  and  Illinois  appear  to  be  the  only  states 
which  have  made  progress  in  building  roads  of  brick.  Cuyahoga  County, 
Ohio,  stands  first  in  mileage  of  brick  roads. 

EXPENDITURES.  The  total  expenditures  for  public  roads  during  1904, 
by  states,  counties,  townships,  and  districts,  from  property  and  poll 
taxes,  bond  issues,  and  state-aid  funds,  together  with  the  valuation  of 
the  labor  expended  under  the  statute-labor  law,  amounted  to  $79,771,- 
417.87,  not  including  Indian  Territory,  Alaska,  or  our  island  possessions. 

Of  this  amount  $53,815,387.98  was  expended  from  property  and  poll 
taxes  payable  in  cash,  $19,818,236.30  was  the  value  of  the  labor  taxes, 
$3,530,470.93  came  from  bond  issues,  and  $2,607,322.66  was  expended 
from  state-aid  funds.  By  comparing  the  total  expenditures  in  all  the 
states  and  territories  with  the  total  mileage  of  all  public  roads  and  with 
the  total  population  of  the  United  States,  it  is  found  that  the  expenditures 
for  road  purposes  amounted  to  $37.07  per  mile  of  public  road,  or  $1.05 
per  inhabitant. 

As  a  bridge  is  usually  considered  a  part  of  a  road,  and  as  taxes  are,  in 
most  cases,  levied  and  assessed  for  both  at  the  same  time,  it  was  im- 
practicable to  separate  road  and  bridge  expenditures,  except  in  the  state 
of  New  York,  and  the  total  expenditures  for  roads  has  therefore  been 
made  to  include  those  for  bridges. 

The  amount  which  was  expended  on  public  roads  in  the  United  States 
in  1904  would  represent  the  interest  on  $1,994,285,446.25,  if  computed 
on  a  basis  of  4  per  cent.  When  it  is  considered  that  the  expenditure 
which  this  vast  sum  represents  was  for  the  construction  and  maintenance 
of  2,151,570  miles  of  public  highways,  enough  roads  to  reach  around  the 
earth  at  the  equator  86  times,  it  is  somewhat  surprising  that  the  expend- 
iture was  not  greater. 

A  comparison  which  is  more  to  the  point  is  that  the  National  Govern- 
ment spent  in  the  fiscal  year  1903-4,  $82,372,360.10  for  deepening  the 
waterways,  which  is  about  1.3  times  as  much  as  was  expended  by  all  the 
states,  counties,  townships,  and  districts  in  the  United  States  for  the 
construction  and  maintenance  of  all  the  public  highways. 


APPENDIX  V 
BIBLIOGRAPHY   OF   ROADS,   STREETS,   AND   PAVEMENTS 

THE  following  list  of  books,  government  pamphlets,  etc.,  has  been 
compiled  from  various  sources,  the  selection  being  made  for  the  his- 
torical and  practical  value  of  the  works.  Many  British  parliamentary 
reports,  American  and  foreign  government  bulletins,  and  books  in 
foreign  languages  have  been  omitted,  partly  on  account  of  their 
inaccessiblity  and  their  comparatively  limited  usefulness  and  partly 
in  order  to  bring  the  list  within  reasonable  limits. 

For  convenient  reference,  the  list  is  divided  into  three  sections,  (1) 
Previous  to  1800;  (2)  1800  to  1899;  (3)  1900  to  date,  the  latter  period 
including  practically  all  the  works  of  current  value,  and  in  many  cases, 
brief  descriptive  notes  are  added  to  indicate  something  of  the  scope 
of  the  book.  Also  short  lists  of  the  principal  works  on  such  allied 
subjects  as  Highway  Bridges,  Earthwork,  Tunnels,  and  Forestry  are 
given. 

The  publishers,  or  the  author,  will  be  pleased  to  give  further  informa- 
tion, to  anyone  desiring  it,  of  any  of  these  works  regarding  which  such 
information  is  available. 

SECTION   I,— PREVIOUS   TO    1800 

1583.  Lambard,  William. — The  Duties  of  Constables  .  .  .  Surveyours  of 
the  Highwaies,  &c.  Further  editrons:  1584,  1587,  1594,  1599, 
1602,  1606,  1610. 

1610.  Proctor,  Thomas. — A  Profitable  Worke  to  this  Whole  Kingdome 
concerning  the  Mending  of  all  Highways,  as  also  for  Waters 
and  Iron  Workes. 

1625.  Norden,  John. — An  Intended  Guyde,  for  English  Travailers,  Shew- 
ing in  Generall  how  Far  one  Citie,  and  Many  Shire-Tounes  in 
England,  are  Distant  from  Other. 

This  book  bears  witness  to  the  existence  of  a  "Dark  Age"  period  in  the 
history  of  English  roads,  when  milestones  were  unknown  and  unthought 
of,  since  at  the  foot  of  every  page  is  printed  the  legend  "  Bear  with  Defects." 
The  distances  were  calculated,  with  some  curious  results,  from  the  rude 
maps  then  in  use. 

1635.  -  — . — A  Direction  for  the  English  Traviller  by  which  he 

shall  be  Inabled  to  Coast  about  all  England  and  Wales. 

Contains  a  reference  to  the  existence  of  sign  posts  and  is  an  improve- 
ment over  Norden's  former  book,  having  a  small  circular  map  of  England, 
and  miniature  outline  drawings  representing  the  various  counties. 

505 


506  THE  ART  OF  ROADMAKING 

1641.  Layer,  John. — The  Office  and  Duty  of  Constables  .  .  .  with  the 
Office  of  Surveyors  of  the  Highways. 

1671.  Broadsheet  against  New  Buildings.  A  Proclamation  Respecting 
Highways. 

1675.  Mace,  Thomas. — Profit,  Conveniency,  and  Pleasure  to  the  whole 
Nation:  Being  a  short  Rational  Discourse  .  .  .  concerning  the 
Highways  of  England. 

1675.  Ogilby,  John. — Britannia,  or  an  Illustration  of  the  Kingdom  of 
England  and  Dominion  of  Wales,  by  a  Geographical  and  His- 
torical Description  of  the  Principal  Roads  thereof. 

The  first  road  book  from  an  accurate  survey,  the  measurements  being 
taken  by  means  of  a  wheel,  with  a  dial  attached,  for  recording  the  number 
of  revolutions  made.  This  book  was  so  excellent  that  it  formed  the  basis 
of  many  editions  for  a  century  afterwards. 

1682.  The  Infallible  Guide  to  Travellers,  giving  a  most  exact  account  of 

the  four  Principal  Roads  of  England. 

1683.  J.  M. — The  Traveller's  Guide  and  the  Country's  Safety,  Being  a 

Declaration  of  the  Laws  of  England  against  Highwaymen  and 
Robbers  upon  the  Road;  what  is  requisite  and  necessary  to  be 
done  by  such  persons  as  are  robbed  in  order  to  the  recovering 
their  damages;  against  whom  they  are  to  bring  their  action; 
and  the  manner  how  it  ought  to  be  brought. 

1692.  Littleton,  E. — Proposal  for  Maintaining  and  Repairing  the  High- 
ways. 

1694.  Mereton,  George.— A  Guide  to  Surveyors  of  the  Highways  in  their 
Duty. 

1696.  Mather,  William. — Of  Repairing  and  Mending  the  Highways. 

1697.  Dfaniel    De]    F[oe].— An   Essay   upon    Projects;     "Of    the    High- 

ways." 
1712.  Bergier,  Nicholas  (Translation  from).— The  General  History  of  the 

Highways  in  all  Parts  of  the  World,  more  particularly  in  Great 

Britain.      Ch.  XXX:    "The  Fabulous  and  the  True  History  of 

the  Highways  in  England." 
1715.  [Signed  J.  P.]— Mending  the  Roads  of  England. 

1718.  The  Laws  concerning  Travelling. 

1719.  Gardner,  L.— A  Pocket  Guide  to  the  English  Traveller,  being  a 

Complete  Survey  and  Admeasurement  of  the  principal  Roads,  &c. 

1720.  The  Office  and  Duty  of  ...  Surveyors  of  Highways,  Bridges,  and 

Causeways  in  Ireland. 

1724.  [Watts,  John.]— A  List  of  the  Subscribers  for  Mending  the 
Road  from  Reading  to  Caversham,  with  an  account  of  how  the 
money  has  been  laid  out. 

1726.  The  Complete  Parish  Officer;  containing  the  Authority  and  Pro- 
ceedings of  ...  Surveyors  of  Highways. 

1734.  A  Short  Specimen  of  a  New  Political  Arithmetic  containing  some 
Considerations  concerning  Public  Roads.  By  an  F.R.S. 


BIBLIOGRAPHY  OF  ROADS  507 

1737.  Phillips,  Robt. — A  Dissertation  concerning  the  Present  State  of  the 

Highroads  of  England,  especially  of  those  near  London. 
1745.  Nelson,  W. — Office  and  Authority  of  a  Justice  of  the  Peace,  shewing 

also  the  Duty  of  ...  Surveyors  of  the  Highways. 

1745-6.  Newball,  John. — A  Concern  for  Trade,  and  the  Various  Conse- 
quences relating  to  the  Encrease  and  Decrease  and  the  Equal 

and  Unequal  Circulation  of  Trade. 

1748.  Defoe,  Daniel. — A  Tour  through  the  whole  Island  of  Great  Britain. 
1740.  Shapleigh,  John. — Highways:    A  Treatise  showing  the  Hardships 

and  Inconveniences  of  Presenting  or  Indicating  Parishes,  Towns, 

&c.,  for  not  Repairing  the  Highways. 
1750.  Collier,  James. — Remarks  on  Road  Bills  in  General,  and  on  the 

Wisbech  Road  Bill  in  Particular. 
1753-  Proposals  at  large  for  the  Easy  and  Effectual  Amendment  of  the 

Roads  by  some  further  Necessary  Laws  and  Regulations.     By  a 

Gentleman. 
1756.  A  New  and  Accurate  Description  of  the  Present  Great  Roads  and 

the  Principal  Cross  Roads  of  England  and  Wales. 
1756.  An  Appendix;    or  Further  Reasons  in  Support  of  of  the  Plan  or 

Proposals  for  the  Amendment  of  the  Roads  by  Way  of  Answer 

to  Several  Objections.     By  a  Gentleman. 
1763.  Bourn,  Daniel. — A  Treatise  upon  Wheel  Carriages. 

1763.  Hawkins,  John  (afterwards  Sir). — Observations  on  the  State  of  the 

Highways,  and  on  the  Laws  for  Amending  and  Keeping  them  in 
Repair. 

1764.  Burn,  Rev.  Richard. — History  of  the  Poor  Laws. 

1765.  Homer,  Henry. — Inquiry  into  the  Means  of  Preserving  and  Improv- 

ing the  Public  Roads. 
1765.  Whitworth,  R. — Some  Remarks  upon  a  Plan  of  a  Bill  Proposed  to 

Parliament  for  Amending  the  Highways  by  Assessment  instead 

of  Six  Days'  Labour. 
1768.  [Young,  Arthur.] — A  Six  Weeks'  Tour  through  the  Southern  Counties 

of  England. 

1770.  -  — . — A  Six  Months'  Tour  through  the  North  of  England. 

Second  Edition.     Four  vols. 

1771.  -  — . — The  Farmers'   Tour  through   the  East  of  England. 

Four  vols. 

1771.  Paterson,  Daniel,  Lt.-Col. — A  New  and  Accurate  Description  of  all 
the  Direct  and  Principal  Cross  Roads  in  Great  Britain.  Second 
Edition,  1773.  Sixteenth  Edition,  1822. 

1771.  Whitworth,   Sir  Charles. — Observations  on  the  new  Westminster 

Paving  Act. 

1772.  [Collection  of  Acts  of  Parliament  relating  to  Roads  in  Surrey  and 

Sussex,  1717-1770]. 

1772.  Acts  relative  to  the  Roads  leading  from  Westminster  and  Black- 
friars  Bridges  (1750-1768),  with  Index. 


508  THE  ART  OF  ROADMAKING 

1773.  Bayley,  Thos.  Butterworth. — Observations  on  the  General  Highway 
and  Turnpike  Acts. 

1773-  Jacob,  J. — Observations  on  the  Structure  and  Draught  of  Wheel 

Carriages. 

1773.  Bourn,  Daniel. — Some  Brief  Remarks  upon  Mr.  Jacob's  Treatise  on 

Wheel  Carriages. 

1774-  Jacob,  Joseph. — Animadversions  on  the  Use  of  Broad  Wheels,  and 

the  Preservation  of  the  Public  Roads. 

1774.  Postlethwaite's  Dictionary. — Roads. 

1776.  Mostyn,  John  Armstrong. — An  Actual  Survey  of  the  Great  Post 
Roads  between  London  and  Edinburgh. 

1778.  Scott,  John. — Digests  of  the  General  Highways  and  Turnpike  Laws. 

1782.  Bowles's  Post-Chaise  Companion;  or  Travellers'  Directory  through 
England  and  Wales.  Being  an  Actual  Survey  of  all  the  Direct 
and  Principal  Cross  Roads,  with  the  Milestones  Expressed  as 
they  Stand  at  Present.  Two  Volumes.  Second  Edition. 

1787.  Godschall,  John. — A  General  Plan  of  Parochial  Police. 

1787.  Paterson,  Daniel,  Lieut.-Col. — A  Travelling  Dictionary;  or  Alpha- 
betical Tables  of  the  Distance  of  all  the  Principal  Cities,  Borough, 
Market,  and  Seaport  Towns,  in  Great  Britain  from  each  Other, 
Comprehending  about  Fifty  Thousand  Distances.  Fifth  Edition. 

1790.  Anstice,  Robert. — Remarks  on  the  Comparative  Advantages  of 
Wheel  Carriages  of  Different  Structure  and  Draught. 

1792.  Newton,  Everard. — The  Whole  Duty  of  Parish  Officers,  containing 
all  the  Laws  now  in  force  relative  to  ...  Surveyors  of  High- 
ways. 

1792.  The  Road  from  the  Port  of  Milford  to  the  Severn. 

1794-1810.  Board  of  Agriculture. — Many  Volumes  of  Surveys  of  Counties, 
containing  incidental  accounts  of  Roads  and  Road  Maintenance. 

1795.  Metcalf,  John.— The  Life  of  John  Metcalf. 

1797.  Gumming,  Alexander. — Observations  on  the  Effects  which  Carriage 

Wheels,  with  Rims  of  Different  Shapes,  have  on  the  Roads. 

1798.  Gary,  John. — Gary's  New  Itinerary;  or  an  Accurate  Delineation  of 

the  Great  Roads  throughout  England  and  Wales,  with  many  of 
the  Principal  Roads  in  Scotland,  from  Actual  Admeasurement. 
The  Eleventh  Edition,  with  improvements,  appeared  in  1828. 

First  made  by  command  of  his  Majesty's  Postmaster-General  for  official 
purposes  in  connection  with  the  mail  coaches.  Some  of  the  southern  cross 
roads  were  measured  by  a  peculiar  method,  since  the  compiler  engaged 
the  services  of  George  Wilson,  a  celebrated  pedestrian,  who  claimed  to 
estimate  distances  most  exactly  by  the  time  occupied  in  walking  from  one 
place  to  another. 

1798.  The  Duty  of  Surveyors  of  Highways,  in  a  Charge  to  be  Delivered 

to  them  at  their  Appointment,  being  first  Signed  and  Sealed  by 
the  Justices  in  their  Petty  Sessions.  By  a  County  Magistrate. 
Another  edition,  1807. 

1799.  The  Surveyor's  Appointment  and  Guide.     Sixth  Edition. 


BIBLIOGRAPHY  OF  ROADS  509 


SECTION    II.— 1800-1899 

1800.  Report   of  a   Committee   of   Trustees   of   the   Hammersmith   and 

Brentford  Turnpikes. 

1 80 1.  [Barry,  J.  B.] — The  Laws  respecting  Highways  and  Turnpike  Roads. 
1805.  Owen,  William. — A  new  Book  of  Roads,  or  a  Description  of  the 

Roads  of  Great  Britain.     Other  Editions,  1808,  1827. 

1808.  Report  of  the  Secretary  of  the  Treasury  on  the  Subject  of  Public 

Roads  and  Canals. 

1809.  Gumming,  Alexander. — A  Supplement  to  the  Observations  on  the 

Contrary  Effects  of  Cylindrical  and  Conical  Carriage  Wheels. 

1811.  Bird,  J.  G. — The  Laws  respecting  Travellers  and  Travelling,  com- 
prising all  the  Cases  and  Statutes,  &c.  Second  Edition.  Another 
Edition,  1819. 

1811.  Duane,  William  J.  (1780-1865).— Letters,  addressed  to  the  People 
of  Pennsylvania  Respecting  the  Internal  Improvement  of  the 
Commonwealth  by  Means  of  Roads  and  Canals. 

1813.  Edgeworth,  Richard  L.  (1744-1817). — An  Essay  on  the  Construction 

of  Roads  and  Carriages. 

1814.  Melish,   John   (1771-1822).— A  Description   of  the  Roads  of  the 

United  States. 

1816.  Bird,  J.  G. — The  Laws  respecting  Highways  and  Turnpike  Roads,  of 

Changing,  Stopping,  and  Repairing  Highways,  &c.    Third  Edition. 

1817.  Edgeworth,  R.  L. — An  Essay  on  the  Construction  of  Roads  and 

Carriages. 

1818.  Clarke,  James. — Practical  Directions  for  Laying  Out  and  Making 

Roads. 

1818.  Dupin,  Baron  Charles. — Memoires  sur  la  Marine  et  les  Ponts  et 
Chaussees  de  France  et  de  1'Angleterre. 

1818.  Greig,  William. — Strictures  on  Road  Police,  containing  Views  of 

the  Present  System  on  which  Roads  are  Repaired. 

1819.  Communication   to   the    General    Assembly   of   Maryland    on   the 

Subject  of  Turnpike  Roads. 

1819.  Macadam,  John  Loudon. — A  Practical  Essay  on  the  Scientific 
Repair  and  Preservation  of  Public  Roads. 

1819.  Report  of  the  Secretary  of  War  Relative  to  Roads  and  Canals. 

1820.  Egremont,  John. — The  Law  relating  to  Highways,  Turnpike  Roads, 

Public  Bridges,  and  Navigable  Rivers.     Two  vois. 

1820.  Fry,  Joseph  Storrs  (d.  1815). — An  Essay  on  the  Construction  of 
Wheel  Carriages  as  they  Effect  both  the  Roads  and  the  Horses. 

1820.  General  Rules  for  Repairing  Roads.  Published  by  Order  of  the 
Parliamentary  Commissioners  for  the  Improvement  of  the  Mail 
Coach  Roads  from  London  to  Holyhead,  and  from  London  to 
Liverpool,  for  the  Use  of  the  Surveyors  to  these  Roads.  Third 
Edition. 


510  THE  ART  OF  ROADMAKING 

1821.  The  Improvement  of  the  Public  Roads  urged  during  the  Existing 
Dearth  of  Employment  for  the  Poor. 

1821.  Macadam,  John  Loudon   (1756-1836). — Remarks  on  the    Present 

System    of    Road-Making,    with    Observations    deduced    from 
Practice  and  Experience.     Further  Editions,  1823,  1827. 

1822.  Bateman,  Joseph. — The    General    Turnpike  Road  Act.      Another 

edition,  1852. 

1822.  [A  Clerk  to  Trustees.] — A  Digest  of  the  Laws  relating  to  Turnpike 
Roads. 

1822.  Dupin,  Baron  Charles  (1784-1873). — Application  de  Geometric  et  de 

Me"chanique,  a  la  Marine,  aux  Ponts  et  Chaussees. 

1823.  Cordier,    Joseph    L.    Etienne    (1775-1849). — Ponts    et    Chaussees. 

Essais  sur  la  Construction  des  Routes,  etc. 
1823.  Bateman,  Joseph. — A  Supplement  to  the  General  Turnpike  Road 

Act  of  3  Geo.  IV. 

1823.  Dehany,  William  K.— The  General  Turnpike  Acts. 
1823.  Locker,  E.  H. — Report  on  the  State  and  Condition  of  the  Roads 

and  Mines  on  the  Estate  of  Greenwich  Hospital  in  the  Counties 

of  Cumberland,  Durham,  and  Northumberland. 
1823.  Markland,  J.  H. — On  the  Early  Use  of  Carriages  in  England,  and 

on  the  Modes  of  Travelling. 
1823.  Wake,   Bernard  John. — Turnpike  Roads:     Lenders   of   Money   on 

Mortgage  of  Tolls,  &c. 

1823.  Statement  concerning  the  Thirsk  and  Yarm  Road  by  the  Com- 

mittee of  Trustees. 

1824.  A  Collection  of  Acts  of  Parliament  now  in  Force  for  Regulating  the 

Turnpike  Roads  in  England. 

1824.  Cobbett,  William,  Jun. — The  Law  of  Turnpikes.     Commentaries  on 
the  General  Acts  relative  to  the  Turnpike  Roads  of  England. 

1824.  Dupin,    Baron    Charles    (1784-1873). — Voyages    dans    la    Grande 

Bretagne.     Vols.  V.  and  VI.:    Troisieme  Partie,  Force  Commer- 
ciale,  Tome  Premier,  Voies  Publiques. 

1825.  Dupin,    Baron    C. — Commercial    Power    of    Britain.  .  .  .  Streets, 

Roads,  Canals,  Aqueducts,  Bridges,  Coasts,  and  Maritime  Ports. 

Translated  from  the  French.     Two  vols. 
1825.  Highways  Improved. 
1825.  Macadam,  J.  L. — Observations  on  the  Management  of    Trusts  for 

the  Care  of  Turnpike  Roads. 

1825.  Statement  of  the  General  Laws  respecting  Highways  and  Turnpike 

Roads. 

1826.  Ipswich  Turnpike.     General  Statement  of  the  Income  and  Expendi- 

ture between  the  30th  August,  1825,  and  the  30th  August,  1826. 

1826.  Bateman,  Joseph.— Metropolitan  Turnpike  Act. 

1827.  [Bateman,  Joseph]. — A  Second  Supplement  to  the  General  Turn- 

pike Road  Acts. 

1828.  Delane,  W.  F.  A.— Arrangement  of  the  Turnpike  Acts. 


BIBLIOGRAPHY  OF  ROADS  511 

1828.  A  Collection  of  Acts  of  Parliament  now  in  force  for  regulating 

Turnpike  Roads  in  England. 

1829.  Wellbeloved,  R. — Treatise  on  the  Law  relating  to  Highways. 

1829.  Woolrych,  H.  W.— A  Treatise  on  the  Law  of  Ways. 

1830.  A  Plan  of  the  Intended  Turnpike  Road  from  Saint  Marylebone 

into  the  Great  North  Road.     (Prospectus  and  Map.) 
1830.  Broadsheet,  printed   by  J.  Catnach.     The  New    Invented    Steam 

Carriage,  with  Woodcut  of  Two  Steam  Carriages  Travelling  on 

the  Road,  also  Explanation,  Full  Account,  and  a  "New  Song'* 

on  the  Subject. 
1830.  Saco,  Jose*  Antonio  (1800-1879). — Memoria  sobre  Caminos,  en  la 

Isla  de  Cuba. 
1832.  Index  to  the  General  Turnpike  Act  for  Scotland. 

1832.  Phillips,  Sir  Richard.— A  Million  of  Facts  in  the  Entire  Circle  of  the 

Sciences,  &c. 

Frontispiece  of  the  Steam  Carriage  Running  from  Paddington  to  the 
Bank  of  England,  1832,  and  particulars  of  other  steam  coaches  running  on 
the  roads  from  London. 

1833.  MacNeill,  Sir  John,  LL.D.— Tables  for  Calculating  the  Cubic  Quan- 

tity of  Earthwork  in  the  Cuttings  and  Embankments  of  Canals, 

Railways,  and  Turnpike  Roads.    Second  Edition,  Enlarged.    1846. 
1833.  Parnell,  Henry  Brooke  (Baron  Congleton) .— A  Treatise  on  Roads. 
1833.  Aldborough    Turnpike.     General    Statement    of    the    Income    and 

Expenditure  between  the  15th  September,  1832,  and  the  16th 

September,  1833. 

1833.  Ipswich  Turnpike.     General  Statement  of  the  Income  and  Expendi- 

ture between  30th  August,  1832,  and  30th  August,  1833. 

1834.  Mills,  Robert. — Substitute  for  Railroads  and  Canals;    Embracing 

a  New  Plan  of  Roadway. 

1834.  Grahame,  Thomas. — Treatise  on  Internal  Intercourse  in  Civilised 
States,  particularly  in  Great  Britain. 

1834.  Gamier,  Francois  Xavier  P.  (1793-1879).—  Traite*  des  Chemins  de 

toute  Espece. 

1834-  Penfold,  Charles  (1799-1864).— A  Practical  Treatise  on  the  Best 
Modes  of  Making  Roads. 

1835.  Bateman,  Joseph.— The  General  Highway  Act,  1835. 
1835.  Bramwell,  George. — New  Code  of  General  Turnpike  Acts. 

1835.  Delane,  W  F.  A.— The  Present  General  Laws  for  Regulating 
Highways  in  England. 

1835.  Shelf ord,  Leonard.— The  General  Highway  Act  of  5  and  6  William 
IV.  Another  edition,  1845. 

1835.  Ipswich  Turnpike.  General  Statement  of  the  Income  ahd  Expendi- 
ture between  the  1st  day  of  January  and  31st  December,  1834. 

7835.  Navier,  Claude  L.  M.  H.  (1785-1836).— Considerations  sur  les  Prin- 
cipes  de  la  Police  de  Roulage  et  sur  les  Travaux  d'entretien  des 
Routes. 


512  THE  ART  OF  ROADMAKING 

1836.  The  Office  of  Surveyor  of  the  Highways.     By  a  Magistrate. 
1836.  Barclay,  H.— The  Law  of  the  Road. 

1836.  Fry,  A.  A. — A  Familiar  Abridgement  of  the  General  Highways  Act. 

1837.  Leigh's  Road  Book. 

1837.  Pratt,  John  Tidd. — The  General  Turnpike  Road  Acts. 
1837.  Woolrych,  H.  W. — New  Highway  Act,  5  and  6  William  IV.,  with 
Notes.     Second  Edition. 

1837.  Report  of   the   Chief   Engineer  of   the  State  of  Tennessee  on  the 

Surveys  .  .  .  for  the  Central  Turnpike. 

1838.  Bloodgood,  Simeon  DeWitt. — A  Treatise  on  Roads;    their  History, 

Character  and  Utility. 

1838.  Report  of  the  Street  Committee  (New  York  City)  Upon  the  Resolu- 
tion on  Continuing  the  Wooden  Pavement  in  Broadway,  and  the 
Relative  Merits  of  Macadamizing  and  Wood  for  Paving  Streets. 

1838.  Hughes,  Thos. — The  Practice  of  Making  and  Repairing  Roads. 

1838.  Rickman,  John,   Edited  by. — Life  of  Thomas  Telford,   Esq.     By 

Himself. 

1839.  The  Roads   and   Railroads,   Vehicles  and  Modes  of  Traveling  of 

Ancient  and  Modern  Countries;  With  Accounts  of  Bridges, 
Tunnels  and  Canals  in  Various  Parts  of  the  World. 

1841.  Husson,  Armand  (Jean  Christophe  Armand)  (1809-1874).— Traite 
de  la  Legislation  des  Travaux  Publics  et  de  la  Voirie  en  France. 

1841.  An  Abstract  of  Accounts  for  14  Years  ending  Whitsuntide,  1840 
...  of  the  Pious  Uses  Trustees  .  .  .  Published  by  Order  of  the 
Board  of  Surveyors  of  Highways  for  the  Township  of  Leeds. 

1843.  Bayldon,  Richard. — Suggestions  for  Consolidating  the  Funds  and 
Management  of  Turnpike  Roads,  and  Management  within  the 
Borough  of  Leeds. 

1843.  Bayldon,  Richard. — Remarks,  with  a  Tabular  Statement,  showing 
the  Operation  of  the  19th  Clause  of  the  proposed  General  Turn- 
pike Bill  on  the  Roads  within  the  Borough  of  Leeds;  with  an 
Appendix  ...  on  Road  Management. 

1843.  B.,  J.  F.  [Burgoyne,  J.  F.] — Remarks  on  the  Maintenance  of  Macad- 
amised Roads. 

1843.  Lee,  Wm. — On  Modern  Carriage  Ways. 

1843.  Report  on  the  Patent  Road  Cleansing  Machine  (of  Sir  Joseph 
Whitworth). 

1843.  Road  Work  on  Railways.  A  Statement  made  by  the  Trustees  of 
the  Cheltenham  District  of  Turnpike  Roads. 

1843.  Simons,  Frederic  W.  (1803-1865).— Treatise  on  the  Principles  and 

Practice  of  Levelling  .  .  .  principally  in  the  Construction  of 
Roads;  with  Mr.  Telford's  Rules  for  the  Same.  (New  Edition, 
1870). 

1844.  Leahy,  E. — On  Making  and  Repairing  Roads. 

184^.  Pratt,  J.  Tidd.— The  Law  relating  to  Highways,  &c.  Fourth 
Edition. 


BIBLIOGRAPHY  OF  ROADS  513 

1845.  Pagan,  Wm. — Road  Reform  (in  Scotland). 

1845.  Isle  of  Wight  System  of  Roads  and  System  of  Guardians  of  the 

Poor  not  a  Model  but  a  Warning  to  the  Legislature. 
1847.  Balydon,  Richard.— Turnpike  Traffic  and  Tolls. 
1847.  Ricardo,  David. — Rebecca  at  Stroud:    or  a  Few  Words  about  the 

Turnpike  Trusts. 
1847.  Gillespie,  W.  M. — Principles  and  Practice  of  Road  Making.     (New 

York.) 
1850.  Law,  H.— Rudiments  of  the  Art  of  Constructing  and  Repairing 

Common  Roads. 
1850.  Report  of  the  Secretary  of  State   (N.  Y.  State)   of  Plank  Road 

Statistics  of  New  York. 

1850.  Owen,  Robert  Dale  (1801-1877). — Treatise  on  the  Construction  and 

Management  of  Plank  Roads. 

1851.  Kingsford,  William  (1819-1898). — History,  Structure  and  Statistics 

of  Plank  Roads. 

1851.  Gregg,  William. — Essay  on  Plank  Roads. 

1852.  The  Highway  Surveyor's  Guide. 

1853.  Whitworth,    Sir    Joseph. — On   the    Advantages   and    Economy    of 

Maintaining  a  High  Degree  of  Cleanliness  in  Roads  and  Streets. 

1853.  Gillespie,  William  M.  (1816-1868).— Manual  of  the  Principles  and 

Practice  of  Road  Making;    comprising  the  Location,  Construc- 
tion, and  Improvement  of  Roads  and  Rail-roads. 

1854.  Bateman,  Joseph,  and  Welsby,  W.  N. — The  General  Turnpike  Road 

Acts. 

1854.  Oke,  George  C. — The  Laws  of  Turnpike  Roads;  practically  arranged, 

with  Cases,  Notes,  Forms,  &c.     Second  Edition,  1860. 

1855.  Nicholson,  Samuel. — The  Nicholson  Pavement.     (Second  Edition, 

1859). 

1857.  Bayldon,  Richard. — Treatise  on  Road  Legislation  and  Management. 
1860.  Bella,  Giuseppe. — Cenni  sui  Lavori  Esequiti  per  le  Nuove  Strade 

Nazionali  Nell'  Isola  di  Sardegna. — Torino,  Italy.     (The  Roads 

of  Sardinia.) 

1860.  Glen,  William  Cunningham.— A  Treatise  on  the  Laws  of  Highways. 

1 86 1.  Laws  of  the  State  of  Michigan  Relative  to  Highways  and  Bridges. 
1 86 1.  Rogers,   Fairman   (1833-1900).— Lectures  on  the  Construction  of 

Roads  and  Bridges. 
1 86 1.  Burgoyne,  Sir  J.  F.,  and  Mallet,  R. — The  Art  of  Constructing  Roads. 

1861.  Smiles,    Samuel    (1812-1904).— Lives   of   the   Engineers.     Vol.    I., 

Part   III.:     Early   Roads  and   Modes   of  Travelling.     Vol.    II., 
Part  VIII.:   Life  of  Thomas  Telford.     (Second  Edition,  1867). 

1862.  Glen,  William  Cunningham. — The  Act  for  the  Better  Management 

of  Highways.     Other  editions  1863,  1864,  1879. 

1863.  Medley,  Julius  George. — Roads — Roorkee,  India. 

1863.  Barclay,  H. — Law  of  Highways  in  Scotland.     Fourth  Edition. 
1863.  Bateman,  Joseph. — The  General  Highway  Acts. 


514  THE  ART  OF  ROADMAKING 

1863.  Exemplification  of  Glen's  Highway  Board  Accounts. 

1863.  Owston,  H.  A. — Highway  Laws. 

1864.  Glass,  Henry  Alexander. — Lectures  on  Roads  and  Roadmakers. 

1864.  Owston,  H.  A.— Highway  Acts  of  1862  and  1864.     Second  Edition. 

1865.  Glen,  W.  Cunningham. — The  Law  of  Highways.      Other  editions 

1885. 

1866.  Planta,    Peter    C.    (1815-         ).— Die    Bunder    Alpenstrassen. — St. 

Gallen,  Switzeland. 

1867.  Johnson,   Frank   G.    (1835-       ). — The   Nicholson   Pavement,    and 

Pavements  Generally. 

1868.  Beckwith,  Arthur. — Report  on  Asphalt  and  Bitumen,  as  Applied 

to  the  Construction  of  Streets  and  Sidewalks  in  Paris. 
1868.  [Various  Authors]. — Rudimentary  Papers  on  the  Art  of  Constructing 

and  Repairing  Common  Roads. 
1870.  Herschel,  C.,  Milla,  S.  F.,  Onion,  H. — Prize  Essays  on  Roads  and 

Road  Making. 

1870.  Paget,  Fred  A. — Report  on  the  Economy  of  Road  Maintenance  and 

Horse  Draught  through  Steam  Rolling,  with  Special  Reference  to 
the  Metropolis. 

1871.  First  Annual  Report  of  the  Citizens'  Association,  for  the  Improve- 

ment of  the  Streets  and  Roads  of  Philadelphia,  Pa. 

1874.  Browne,  Sir  James  F.  M.  (1823-  ).— On  the  Tracing  and  Con- 
struction of  Roads  in  Mountainous  Tropical  Countries. 

1874.  An  Act  Revising  and  Embodying  all  the  Laws  Authorizing  Post- 
roads,  in  force  December  1,  1873. 

1874.  Hay  wood,  Wm. — Report  on  Accidents  to   Horses  on  Carriageway 

Pavements. 

1875.  Campbell,  John  I.— A  Road  System  in  Statutory  Form,  for  Creating, 

Constructing,  Repairing  and  Maintaining  Public  Highways. 
1875.  Rennie,  Sir  John. — Autobiography. 

1875.  Society  of  Arts. — Report  of,  on  the  Application  of  Science  and  Art 

to  Street  Paving  and  Street  Cleansing  of  the  Metropolis. 

1876.  Gilmore,    Quincy   Adams    (1825-1888).— A    Practical   Treatise    on 

Roads,  Streets,  and  Pavements  (New  York). 

1878.  Chambers,  G.  F.— The  Law  relating  to  Highways. 

1879.  Ludwig  Salvator,   Archduke   of  Austria   (1847-        ).— Die   Kara- 

wanen-strasse  von  A]gypten  nach  Syrien. — Prag,  Austria. 

1879.  Foot,  C.  H.— Consolidated  Abstracts  of  the  Highway  Acts,  &c. 
Second  Edition. 

1879.  Glen,  Alexander.— The  Highway  Acts,  1862-1878,  &c.,  with  Intro- 
duction, &c. 

1879.  Wilkins,  H.  St.  Clair,  Lieut.-General.— Treatise  on  Mountain  Roads. 

1879.  Willcocks,  George  Waller.— Roads  and  Roadways. 

1880.  Allnutt,  Henry.— Wood  Pavements,  as  Carried  Out  on  Kensington 

High  Road,  Chelsea,  &c. 
1880.  Baker,  T.— Law  of  Highways. 


BIBLIOGRAPHY  OF  ROADS  515 

1880.  Cresy. — Encyclopaedia  of  Civil  Engineering. 

1880.  Glen,  Alexander. — The  Powers  and  Duties  of  Surveyors  of  High- 
ways. Other  editions  1881,  1888. 

1880.  Goudy,  Henry,  and  Smith,  William  C. — Local  Government  in 
Scotland.  Deals  with  the  Law  of  Roads. 

1880.  Thropp,  James. — Highways  and  Locomotives  Act,  1878.     Report 

on  Main  Roads  (Lincolnshire). 

1881.  Situacion  de  las  Carreteras  del  Estado — Madrid,  Spain. 

1881  Spearman,  R.  H. — The  Law  relative  to  Highways  in  England  and 
North  Wales. 

1 88 1.  Chambers,  C.  H. — Public  Health  and  Highways. 

1882.  Harcourt,  E.  W. — Maintenance  of  High  Roads. 

1882.  Higgins,  E. — Letters  on  Highway  Legislation. 

1883.  Boulnois,  H.  Percy. — The  Municipal  and  Sanitary  Engineers'  Hand- 

book. 

1883.  Glen,  William  Cunningham  and  Alexander. — The  Law  relating  to 

Highways,  &c.     Another  edition,  1897. 

1884.  Burrows,  A.  J. — The  Maintenance  and  Construction  of  Roads. 

1884.  The  Highway  Laws  of  Indiana. 

1885.  Harris,  S. — The  Coaching  Age.     Chapters  on  Highways. 

1885.  Laws  of  Indiana  Respecting  Highways,  Free  Roads,  and  Free 
Bridges. 

1885.  New  Highway  Law  of  Indiana. 

1886.  Proceedings    of    a    Conference    on     Highway    Management     (at 

Gloucester). 

1886.  Codrington,  T.— Roads  and  Streets.     Encyl.  Britt.,  Vol.  XX. 
1886.  Malo,  Leon. — On  Asphalte  Roadways. 
1886.  Postu,  Burton  Willis.— The  Road  and  the  Roadside.     (New  Edition, 

1893.) 

1886.  Garard,  Louis  F. — Compilation  of  the  Road  Laws  of  the  State  of 

Georgia. 

1887.  Law,    H.,   and   Clark,   D.    Kinnear. — Construction   of   Roads   and 

Streets. 

1887.  Thropp,  J. — Repairs  of  Roads. 

1888.  Glen,  W.  C.— Highway  Surveyor's  Guide.     Second  Edition. 
1888.  Maudslay,  A.— Highways. 

1888.  Proposed  Street  Improvements  in  the  City  of  Brooklyn. 

1889.  Codrington,  T. — Local  Government  Board  Report  on  Road  Main- 

tenance. 
1889.  Jusserand,  J.  J.   (Translated  by  Lucy  Toulmin  Smith). — English 

Wayfaring  Life  in  the  Middle  Ages.     Part  I.:    English  Roads, 

pp.  35-174. 
1889.  Phillips,   J.   E.— The  Local  Government  Act,    1888,   as  it  affects 

Highways. 
1889.  Smith,    Urban. — Maintenance   of   Main   Roads   in   the   County   of 

Hertford. 


516  THE  ART  OF  ROADMAKING 

1889.  Jenks,  Jeremiah  W.  (1856-  ). — Road  Legislation  for  the  Ameri- 
can State. 

1889.  Pope,  Col.  Albert  A.  (1843-1909).— Highway  Improvement. 

1890.  Herskell,  Ferdinand. — Treatise  on  Roads  and  Prohibition. 

1890.  Haupt,  Lewis  M.  (1844-  ). — Country  Roads;  Their  Relations 
to  Other  Lines  of  Communication  and  to  the  State. 

1890.  Love,  Edward  G. — Pavements  and  Roads;  their  Construction  and 
Maintenance. 

1890.  Pope,  Col.  Albert  A. — The  Movement  for  Better  Roads.  The 
Relation  of  Good  Streets  to  the  Prosperity  of  a  City. 

1890.  Dykes,  J.  E.,  and  Stuart,  D. — Roads  and  Bridges  Manual  (Scotland). 

1890.  Smith,  Urban. — The  Country  Roads  of  England. 

1891.  Streets  and  Highways  in  Foreign  Countries — Reports  from  U.  S. 

Consuls  on  Streets  and  Highways  in  their  Several  Districts. 

1891.  Potter,  Isaac  B.— The  Gospel  of  Good  Roads. 

1891.  Bacon,  A.  P.— California  Asphalt:    God's  Natural  Paving  Material. 

1891.  Fletcher,  W. — History  of  Steam  Locomotion  on  Common  Roads. 

1891.  Sydney,  William  Connor. — England  and  the  English  in  the  Eigh- 
teenth Century.  Vol.  II.,  Ch.  XL:  Roads  and  Travelling. 

1891.  Winstone,  Benjamin. — Minutes  of  the  Epping  and  Ongar  Highway 
Trust,  1769-1870. 

1891.  Streets  and  Highways  in  Foreign  Countries.  Reprinted  Reports  of 
the  United  States  Consuls. 

1891.  Philadelphia.     Committte    on    Better    Roads.     Essays    on    Road 

Making  and  Maintenance. 

1892.  Report  of  the  Dept.  of  Public  Works  of  New  York  City  on  Street 

Pavements,  with  Special  Reference  to  Asphalt  Pavements. 
1892.  Whinery,  Samuel  (1845-         ). — The  Effect  of  Street  Paving  on  the 

Value  of  Abutting  Property. 

1892.  Burke,  Milo  D.  (1841-         ).— Brick  for  Street  Pavements. 
1892.  Byrne,  Austin  T.  (1859-         ). — Treatise  on  Highway  Construction. 

(New  Editions,  1896,  1900.) 

1892.  Codrington,  T. — Maintenance  of  Macadamized  Roads. 
1892.  Harper,  C.  G.— The  Brighton  Road. 

1892.  Spinks,  W. — Law  and  Practice  as  to  Paving  Private  Streets. 

1893.  Holmes,  Joseph  Austin   (1859-         ).— Road  Materials  and  Road 

Construction  in  North  Carolina. 

1893.  Potter,  Isaac  B.  —County  Roads:    An  Illustrated  Primer  of  Road- 

Making. 

1894.  Burke,  M.  D.,  C.E.— Brick  for  Street  Pavements.     An  Account  of 

Tests  Made  with  Bricks  and  Paving  Blocks. 

1894.  Wright,  R.  S.,  and  Hobhouse,  Henry.— An  Outline  of  Local  Govern- 
ment, England,  and  Wales.  Second  Edition.  Deals  with  the 
Law  of  Roads. 

1894.  Judson,  William  Pierson  (1849-  ).— City  Roads  and  Pavements 
for  Oswego,  N.  Y. 


BIBLIOGRAPHY  OF  ROADS  517 

1894.  Spalding,    Frederick    P.    (1857-         ). — Text-book    on    Roads   and 

Pavements. 
1894.  Herschel,  C.,  and  North,  E.  P. — The  Science  of  Road-making  .  .  . 

Construction  and  Maintenance  of  Roads. 

1894.  Stone,  Roy.     New  Roads  and  Road  Laws  in  the  United  States. 
1894.  - —        — . — Earth  Roads:  Hints  on  their  Construction  and  Repair. 

(Government  Bulletin.) 
1894. — . — State  Laws  Relating  to  the   Management   of   Roads, 

enacted  in  1888-93.     (Government  Bulletin.) 
1894.  Information    Regarding    Roads    and    Road-making    Materials     in 

Certain  Eastern  and  Southern  States.     (Government  Bulletin.) 
1894.  Information    Regarding    Roads    and    Road    Materials    in    Certain 

States  North  of  the  Ohio  River.     (Government  Bulletin.) 
1894.  Information  Regarding  Road  Materials  in  Certain  States  West  of 

the  Mississippi  River.     (Government  Bulletin.) 
1894.  Sheffield,  0.  H. — Improvement  of    the  Road  System  of  Georgia. 

(Government  Bulletin.) 
1894.  Brauner,    John    Caspar. — Report    on    Road-making    Materials    of 

Arkansas.     (Government  Bulletin.) 

1894.  Ordinances  Concerning  the  Improvement  of  Streets,  Alleys,  Side- 

walks, etc.,  of  Louisville,  Ky. 

1895.  Shaler,    Nathaniel    S.    (1841-1906).— The    Geology    of    the    Road- 
building  Stones  of  Massachusetts. 

1895.  Report  of  the  Joint  Committee  to  Examine  into  the  Condition  of 
the  Roads  and  Public  Highways  of  Rhode  Island. 

1895.  Stone,  Roy. — Best  Roads  for  Farms  and  Farming  Districts;  Cooper- 
ative Road  Construction. 

1895.  -  — . — State  Laws  Relating  to  the  Management  of  Roads; 

Enacted  in  1894-95.  (Government  Bulletin.) 

1895.  — —  -  — . — Historical  and  Technical  Papers  on  Road  Building 
in  the  United  States.  (Government  Builletin.) 

1895.  — • — Good  Roads;  Extracts  from  Messages  of  Governors. 

(Government  Bulletin.) 

1895.  -  — . — Wide  Tires.  Laws  of  Certain  States  Relating  to 

their  Use.  (Government  Bulletin.) 

1895.  Crump,  M.  H. — Kentucky  Highways.  History  of  the  Old  and  New 
Systems.  (Government  Bulletin.) 

1895.  Perkins,  George  Arthur. — State  Highways  of  Massachusetts. 

1895.  Holmes,  Joseph  A. — Improvement  of  Public  Highways  of  North 
Carolina. 

1895.  Shaler,  Nathaniel  S.  (1841-1906). — Preliminary  Report  on  the 
Geology  of  the  Common  Roads  of  the  United  States. 

1895.  Wheeler,  Herbert  A.  (1859-         ).— Vitrified  Brick  Paving. 

1895.  Wallace,  W.  W.,  Jr.— Brick  Pavements. 

1895.  Willmann,  Leo  von  (1848-         ). — Strassenbau. — Leipzig. 

1895.  Boulnois,  H.  P. — The  Construction  of  Carriageways  and  Footways. 


518  THE  ART  OF  ROADMAKING 

1895.  Harper,  C.  G.— The  Dover  Road. 

1895.  -  — . — The  Portsmouth  Road. 

1896.  Hunter,  (Sir)  Robert. — Preservation  of  Open  Spaces  and  Footpaths 

and  other  Rights  of  Way. 

1896.  Petsche,  Albert. — Le  Bois  et  ses  Applications  au  Parage. — Paris. 
1896.  Lefebvre,  Georges  (1860-         ).— Voie  Publique. — Paris. 
1896.  Shaler,  Nathaniel  S. — American  Highways;    a  Popular  Account  of 

their  Condition. 
1896.  Rockwell,  Alfred  P.  (1834-         ). — Roads  and  Pavements  in  France. 

1896.  Neely,  Samuel  T. — Traction  Tests.     (Government  Bulletin.) 

1897.  Merrill,  Frederick  J.  H.   (1861-         ).— Road  Materials  and  Road 

Building  in  New  York. 
1897.  Pratt,   J.    T.,   and   MacKenzie,   Wm.— Pratt's   Law   of   Highways. 

Fourteenth  Edition. 
1897.  Whittle,    C.    L. — The   Forces   which    Operate   to    Destroy   Roads, 

with  Notes  on  Road  Stones  and  Problems  therewith  connected. 

(Government  Bulletin.) 

1897.  Highway    Maintenance     and     Repairs.     Taxation;      Comparative 

Results   of   Labor   and   Money   Systems;     Contract   System    of 
Maintaining  Roads.     (Government  Bulletin.) 

1898.  Laws  of  the  State  of  Illinois  in  Relation  to  Roads  and  Bridges. 

1898.  The  Highway  Law  of  New  York  State. 

1899.  Sioussat,  St.  George  L. — Highway  Legislation  in  Maryland. 
1899.  Cartland,  John  Henry. — Ancient  Pavings  of  Pemaquid,  Me. 
1899.  Eldridge,  Maurice  Owen. — Good  Roads  for  Farmers. 
1899.  -  — . — Construction  of  Good  Country  Roads. 
1899.  Dodge,  Martin.— Steel  Track  Wagon  Roads. 

1899.  Report  on  the  Highways  of  Maryland  (Geographical  Survey). 

1899.  Laws  of  Maryland  Relating  to  Highways. 

1899.  Conder,  J.  B.  R. — Handbook  of  Highway  Cases. 

1899.  Harper,  C.  G.— The  Bath  Road. 

1899.  -  —.—The  Exeter  Road. 

1899.  Maxwell,  W.  H. — The  Construction  of  Roads  and  Streets. 

1899.  Holmes,  J.  A.  (1859-  ).— Some  Recent  Road  Legislation  in 
North  Carolina.  (Government  Bulletin.) 

1899.  Maxwell,  William  H.— The  Construction  of  Roads  and  Streets. 
With  Historical  Sketch  of  the  Development  of  the  Art  of  Road- 
making.  London.  Cloth,  4|X6i  ins.;  256  pages;  illustrated. 
Price,  $1.30. 

A  resume*  of  the  English  practice  in  road-building  and  street  construction* 
with  notes  on  the  character  of  materials,  calculation  of  quantities  and 
the  various  methods  of  systems  now  in  use. 

While  the  work  is  avowedly  a  compilation  from  many  sources,  it  is 
useful  as  a  compilation  of  British  methods  of  road  construction  and  main- 
tenance of  that  time. 

n.  d.    Cook,  John.— Cursory  Remarks  on  Wheeled  Carriages, 
n.  d     Dawson,  G.  F.  Crosby. — Street  Pavements. 


BIBLIOGRAPHY  OF  ROADS  519 

n.  d.    Edgworth,  J. — New  Mode  of  Constructing  Streets. 

n.  d.    Gilbert,  Davies,  M.P.,  F.R.S.— A  Treatise  on  Wheels  and  Springs  for 

Carriages, 
n.  d.    Parry,  A.  W.— The  Use  of  Steam  Rollers. 


SECTION   III.— 1900  TO  DATE 

The  publications  in  this  section  comprise  all  the  works  of  current 
interest    and    many    government    documents.     Each    edition    is    listed 
separately  and  brief  descriptions,  with  prices,  are  given  of  several  stand- 
aid  works  which  can  be  recommended  for  further  study. 
1900.  Allen,   A.   T. — Footpaths:    Their  Maintenance,   Construction,   and 

Cost. 

1900.  Harper,  C.  G. — The  Great  North  Road.     Two  vols. 
1900.  Laws  Relating  to  Roads,  Ferries  and  Bridges  of  Mississippi. 
1900.  Eldridge,  Maurice  Owen. — Progress  of  Road  Building  in  the  United 

States. 
1900.  Elliott,  Byron  K.,  and  Elliott,  William  F.— Treatise  on  the  Law  of 

Roads  and  Streets. 

1900.  Road  Laws  of  the  State  of  Iowa. 

1900.  Aitken,  Thomas. — Road  Making  and  Maintenance.     (Third  Edition) . 
1900.  Tillson,    George    William    (1852-         ). — Street     Pavements    and 

Paving  Materials. 
1900.  Johnson,  Sarah  Alice. — Facts,  Suppositions,  and  Theories,  or  Road 

Mending,  &c. 

1900.  Wheeler,  W.  H. — The  Repair  and  Maintenance  of  Roads. 

1901.  Clemens,  Gasper  C. — Manual  of  the  Laws  of  Roads  and  Highways 

in  the  State  of  Kansas. 

1901.  Road  Laws  of  Oregon. 

1901.  Laws  of  the  State  of  Missouri  Relating  to  Roads,  Highways,  and 
Bridges. 

1901.  Recent  Road  Legislation  in  North  Carolina. 

1901.  Abbott,  James  Whitin. — Mountain  Roads.     (Government  Bulletin.) 

1901.  Pope,  Logan  Waller. — The  Selection  of  Materials  for  Macadam 
Roads  (Government  Document). 

1901.  McCallie,  Samuel  W.  (1856-  ). — Report  on  the  Roads  and  Road- 
building  Materials  of  Georgia. 

1901.  Le  Strade  di  Milano — Milan,  Italy. 

1901.  County  Councils  Association. — A  Digest  of  Answers  to  a  Series  of 
Questions  with  Regard  to  the  Management  of  Main  Roads  and 
Highways. 

1901.  Greenwell,  Allen,  and  Elsden,  James  Vincent. — Roads:  Their  Con- 
struction and  Maintenance,  with  Special  Reference  to  Road 
Materials. 

1901.  Harper,  C.  G.— The  Norwich  Road. 


520  THE  ART  OF  ROADMAKING 

1902.  Laws  of  Iowa  Relating  to  Roads,  Bridges  and  Ferries. 

1902.  Holmes,    Joseph    A. — Roadbuilding    with    Convict    Labor    in    the 

Southern  States.     (Government  Bulletin.) 
1902.  Dodge,    Martin. — Government  Cooperation  in  Object-lesson  Road 

Work.     (Government  Bulletin.) 
1902.  Progress    of    Road    Legislation    and    Road    Improvement    in    the 

Different  States. 
1902.  Abbott,  James  Whitin. — Mountain  Roads  as  a  Source  of  Revenue. 

(Government  Bulletin.) 

1902.    Weicht,  A.  H. — Bau  von  Strassen  und  Strassenbahnen. — Berlin. 
1902.  Judson,  William  Pierson  (1849-         ). — City  Roads  and  Pavements 

suited  to  Cities  of  Moderate  Size.     (Second  Edition.) 
1902.  Spalding,    Frederick    P.    (1857-         ). — Text-book    on    Roads    and 

Pavements.     (Second  Edition.) 
1902.  -  — . — The  Cambridge,  Ely,  and  King's  Lynn  Road. 

1902.  -  — . — The  Holyhead  Road. 

1903.  Connecticut  Law  for  the  Improvement  of  Public  Roads. 

1903.  Laws  of  the  State  of  Missouri  Relating  to  Roads,  Highways  and 
Bridges. 

1903.  Fox,  William  F.  (1840-  ). — Tree  Planting  on  Streets  and 
Highways. 

1903.  Laissle,  Friedrich. — Der  Strassenbau  Einschliesslich  der  Strassen- 
bahnen . —  Leipzig.  * 

1903.  Abbott,  James  Whitin. — Use  of  Mineral  Oil  in  Road  Improvement. 

1903.  Page,  Logan  Waller. — The  Testing  of  Road  Materials.  (Government 
Bulletin.) 

1903.  Buckley,  Ernest  Robertson  (1872-  ). — Highway  Construction  in 
Wisconsin. 

1903.  Baker,  Ira  Osborn  (1853-  ). — Treatise  on  Roads  and  Pavements. 
(First  Edition.) 

1903.  Codrington,  T. — Roman  Roads  in  Britain. 

1903.  Gilbey,  Sir  Walter,  Bart. — Early  Carriages  and  Roads. 

1903.  Jeffreys,  W.  Rees. — Highway  Administration  in  England  and  Wales 
at  the  Beginning  of  the  Twentieth  Century. 

1903.  Latham,  F.— Construction  of  Roads,  Paths,  and  Sea  Defences. 
With  Portions  relating  to  Private  Street  Repairs,  Specification 
Clauses,  Prices  for  Estimating,  and  Engineer's  Replies  to  Queries. 

1903.  Stephens,  J.  E.  R.— Digest  of  Highway  Cases,  with  all  the  chief 
Statutes  on  Highways,  Bridges,  and  Locomotives. 

1903.  Tillson,  George  W. — Street  Pavements  and  Paving  Materials.  A 
Manual  of  City  Pavements;  the  Methods  and  Materials  of  Their 
Construction.  For  the  Use  of  Students,  Engineers  and  City 
Officials.  New  York.  Cloth,  6X9  ins.;  xii  +  532  pages;  60 
illustrations.  Price,  $4.00. 

Contents:  History  and  Development  of  Pavements;  Stone;  Asphalt; 
Bnck-Clays  and  the  Manufacture  of  Paving  Brick;  Cement,  Cement  Mortar 
and  Concrete;  Theory  of  Pavements;  Cobble  and  Stone-Block  Pavements; 


BIBLIOGRAPHY  OF  ROADS  521 

Asphalt  Pavements;  Brick  Pavements;  Wood  Pavements;  Broken-Stone 
Pavements;  Plans  and  Specifications:  Construction  of  Street-Car  Tracks 
in  Paved  Streets;  Width  of  Streets  and  Roadways,  Curbs,  Sidewalks,  etc  ; 
Asphalt  Plants. 

1903.  Latham,    Frank. — The    Construction    of    Roads,    Paths,    and    Sea 

Defences.  With  Portions  relating  to  Private  Street  Repairs, 
Specification  Clauses,  Prices  for  Estimating,  and  Engineers' 
Replies  to  Queries.  London.  Cloth,  6X9  ins.  Price,  $3.00,  net. 

This  book  discusses  the  necessity  of  good  roads  for  traction,  line  of 
roadway,  setting  out,  drainage  and  coverings  of  roads,  road-rolling,  stone- 
breaking,  paving  with  wood,  stone,  brick,  artificial  slabs,  etc.  Short  chap- 
ters also  deal  with  scavenging,  watering,  and  snow  removal  from  roads. 
A  portion  of  the  book  is  devoted  to  sea-walls,  with  illustrations  of  walls  at 
Penzanoe  and  Margate  (England),  and  also  short  chapters  on  road  bridges 
and  artificial  stone  plants.  Useful  specification  clauses  on  roads  and  streets, 
sewers,  and  sea-walls,  and  also  a  table  of  approximate  prices  of  road 
materials,  are  added  at  the  end  of  the  book,  and  in  a  pocket  in  the  cover 
is  a  tabulated  statement  of  details  of  road  construction,  compiled  from 
replies  of  various  engineers  and  of  interest  for  reference. 

1904.  The  New  State  Aid  Road  Law  (Maryland). 

1904.  Maxwell,  William  H. — British  Progress  in  Municipal  Engineering. 

1904.  Beery,  P.  B. — Portland  Cement  Sidewalk  Construction. 

1904.  Page,  Logan  Waller. — The  Cementing  Power  of  Road  Materials. 

(Government  Bulletin.) 
1904.  Craig,  A. — The  Railroads  and  the  Wagon  Roads.     (Government 

Bulletin.) 

1904.  Drummond,  R.,  C.E.,  F.S.A.  (Scot.). — The  Evolution  of  Road 
Making  in  Scotland.  Paper  Read  before  the  Scottish  Auto- 
mobile Club. 

1904.  Fairless,  Michael. — Roadmender.     Re-issue. 
1904.  Ferguson,  James.— The  Law  relating  to  Roads,  Streets,  and  Rights 

of  Way  in  Scotland. 

1904.  Forbes,  N.  A.,  and  Burmester,  A.  C. — Our  Roman  Highways. 
1904.  Hasluck,  Paul  N. — Road  and  Footpath  Construction. 

The  British  and  Irish  Road  Book. — Issued  by  the  Cyclists'  Touring 

Club. 

Vol.  I. — Southern  and  South- Western  Counties.     Sixth  Edition. 
Vol.    II. — Eastern   and    Midland   Counties,    including    Wales. 

Second  Edition.     1898. 

Vol.  III.— Northern  Counties.     Third  Edition.     1899. 
Vol.  IV.— Scotland.     Second  Edition.     1901. 
Vol.  V.— Southern  Ireland.     1899. 
Vol.  VI.— Northern  Ireland.     1900. 

The  most  complete  description  of  British  roads  available  at  the  present 
time,  through  which,  and  similar  volumes  contained  in  this  list,  the  gradual 
growth  of  the  roads  can  be  traced  over  a  period  of  nearly  three  centuries. 

1904.  Spoon,  William  Luther. — Building  Sand-clay  Roads  in  Southern 

States.     (Government  Bulletin.) 
1904.  Richardson,  Robert  W. — Progress  of  Roadbuilding  in  the  Middle 

West.     (Government  Bulletin.) 
1904.  Asphalt  Paving. — Report  of  Commissioners  of  New  York  City. 


522  THE  ART  OF  ROADMAKING 

1905.  Harper,   C.    G.  —  The     Oxford,    Gloucester,     and    Milford    Haven 

Road. 

1905.  Richardson,  Clifford  (1856-         ).  —  The  Modern  Asphalt  Pavement. 
1905.  Wallace,  Henry  (1836-       ).—  How  to  Make  Good  Dirt  Roads. 
1905.  Lancaster,    Sam    C.  —  Practical    Road-building    in    Madison    Co., 

Tennessee.     (Government  Bulletin.) 
1905.  Cushman,  Allerton  S.  —  A  Study  of  Rock  Decomposition  under  the 

Action  of  Water.     (Government  Bulletin.) 
1905.  Manual  for  Iowa  Highway  Officers. 
1905.  Hurlbert,  Archer  Butler  (1873-      ).—  The  Future  of  Road-making 

in  America. 

1905.  Connecticut  Law  for  the  Improvement  of  Public  Roads. 
1905.  Statutes  of  the  State  of  Oregon  Relating  to  Roads,  etc. 
1905.  Road  Laws  of  the  State  of  Idaho. 
1905.  Improvement,  Repair,  and  Maintenance  of  Public  Highways  of  the 

State  of  New  York. 

The  publication  of  this  book  of  instructions  and  suggestions  was  made 
advisable  by  the  numerous  changes  in  the  highway  laws  of  the  State  of 
New  York.  It  sets  forth  a  uniform  system  of  town  accounting  of  highway 
funds  and  also  contains  a  compilation  of  statistics  of  the  cost  and  main- 
tenance of  highways  and  bridges  throughout  the  state. 

1905.  Allen,   A.   Taylor.  —  New  Streets:     Laying   Out   and   Making  Up. 

London.     Cloth,  6X9  ins.;    175  pages.     Price,  $1.20,  net. 

The  purpose  of  this  book  is  chiefly  to  serve  as  a  condensed  form  of 
reference  and  examples  of  carrying  out  the  essential  parts  and  work  entailed 
by  the  British  "Surveyor  under  the  Public  Health  Act"  of  1875,  and  the 
"Private  Street  Works  Act"  of  1892.  It  deals  strictly  with  British  practice. 

1906.  Proceedings  of  the  Good  Roads  Conference  held  at  Denver,  Colo., 

1906. 

1906.  Pennsylvania  Road  Laws. 

1906.  Report  of  Royal  Commission  on  Motor  Cars.  —  London. 
1906.  Guinn,  James  Miller  (1834-         ).  —  El  Camino  Real.    An  Investiga- 

tion into  the  History  of  early  Roads  in  California. 
1906.  Lovegrove,  E.  J.  —  Attrition  Tests  of  Road-making  Stones.     With 

Petrological   Description   by   John   S.    Flett,    M.A.,    D.Sc.,    and 

J.  Allen  Howe,   B.Sc.     London.     Cloth,   8^  +  Hi  ins.;    xix  +  80 

pages;  79  illustrations.     Price,  $2.00. 

These  studies  relate  chiefly  to  specific  rocks  in  Great  Britain,  but  they 
ntain   considerable  information   of   general  interest.     After   a  few  para- 
graphs outlining  the  character  of  his  investigations,    the  author  submits 
tables  giving  attrition  tests   from  a  large  number  of  quarries   and 


contain   considerable  information   of   general  interest.     After   a  few  para- 
utlining the  character  of  his  investigations,    the  author  submits 
taes  gving  attrition  tests   from  a  large  number  of  quarries   and   a  con- 
siderable variety  of  stones.     The  petrological  descriptions  are  classified  by 


granite,  porphyry,  basalt,  and  other  groups,  and  are  accompanied  by 
photomicrographs.  The  descriptions  are  also  supplemented  by  general 
conclusions. 

1906.  Baker,  Ira  0.  (1853-         ).—  Drainage  of  Earth  Roads. 

1906.  Tar  and  Oil  for  Road  Improvement.     (Government  Bulletin.) 

1906.  Spoon,  William  Luther.  —  Construction  of  Sand-clay  and  Burnt-clay 

Roads.     (Government  Bulletin.) 
1906.  Hotchkiss,  William  Otis.  —  Rural  Highways  of  Wisconsin. 


BIBLIOGRAPHY  OF  ROADS  523 

1906.  Gillette,  Halbert  Powers  (1869-  ).— Economics  of  Road  Con- 
struction. Second  Edition,  Enlarged.  Cloth,  6X9  ins.;  49 
pages;  9  illustrations.  Price,  $1.00,  net. 

This  small  book  gives  a  great  deal  of  useful  information  in  clear,  brief, 
and  concise  language.  The  contents  are:  Historical  Review;  Earth  Roads 
and  Earthwork  (Profile  of  Cross-section  of  Road,  Longitudinal  Profile, 
Gutters  and  Drains,  Embankments,  Cost  of  Earthwork,  Surfacing,  Traction 
and  Tractive  Power,  Location);  Gravel  Roads;  Macadam  Roads  (What 
Holds  Macadam  Together,  Quality  of  Stone,  Relative  Wearing  Powers  of 
Stone,  Quarrying,  Dynamite,  Crushing,  Hauling,  Spreading,  Rolling, 
Sprinkling,  Quantity,  and  Cost);  Telford  Roads;  Repairs  and  Maintenance 
(Continuous  vs.  Intermittent  System,  Sandstone  Macadam);  Suggested 
Improvements  in  Existing  Road  Specifications  (Kind  and  Sizes  of  Broken 
Stone,  Depth  of  Pavement,  Final  Surfacing,  Material  for  Embankments, 
Thickness  and  Width  of  Pavements);  Summary  and  Conclusions. 

1906.  Laws  Relating  to  Highways  and  Bridges  of  Michigan.  (Supple- 
ment, 1907). 

1906.  Alien,  A.  Taylor. — Footpaths:  Their  Maintenance,  Construction 
and  Cost. 

1906.  Baker,  Ira  0. — The  Construction  and  Care  of  Brick  Pavements. 

Reprint  of  part  of  a  report  on  "The  Paving  Brick  Industry  of  Illinois," 
prepared  for  the  Illinois  State  Geological  Survey. 

1907.  Lord,  Edwin  C.  E. — Examination  and  Classification  of  Rocks  for 

Road  Building,  Including  the  Physical  Properties  of  Rocks  with 
Reference  to  Their  Mineral  Composition  and  Structure.  (Govern- 
ment Bulletin.) 

This  pamphlet  is  decidedly  technical  in  character,  but  for  engineers  and 
others  who  wish  to  go  thoroughly  into  the  science  of  macadam-road  building 
materials  it  contains  information  of  much  value. 

1907.  Page,  Logan  W. — Object-lesson  Roads.      (Government  Bulletin.) 
1907.  Whinery,  Samuel  (1845-         ). — Specifications  for  Street  Roadway 

Pavements.     New  York.     Paper,  6X9  ins.;  56  pages.     Price,  50 

cents,  net. 

"The  large  and  successful  experience  of  the  author  in  the  construction  of 
pavements,  and  his  studious  habits  and  carefulness  of  language,  make 
any  article  he  may  write  upon  the  subject  of  especial  interest. 

"The  author's  conclusions  respecting  guarantees,  taken  in  connection 
with  the  form  of  the  guarantee  of  work  and  material,  should  meet  with 
general  approval  both  by  municipalities  and  contractors.  .  .  .  The  pam- 
phlet is  a  valuable  contribution  to  the  literature  upon  the  proper  con- 
struction of  pavements." — Engineering  News,  Aug.  15,  1907. 

The  specifications  cover  General  Work,  Foundations,  Bituminous  Pave- 
ments, Granite,  Brick  and  Wood  Block  Pavements. 

1907.  Road  Laws  of  New  Castle  County,  Delaware. 

1907.  Connecticut  Law  for  the  Improvement  of  Public  Roads. 

1907.  Byrne,  Austin  Thomas  (1859-  ). — A  Treatise  on  Highway  Con- 
struction. Designed  as  a  Text-book  and  Work  of  Reference  for 
all  who  may  be  engaged  in  the  Location,  Construction  and 
Maintenance  of  Roads,  Streets  and  Pavements.  Fifth  Edition, 
Revised  and  Enlarged.  New  York.  Cloth,  5fX9£  ins.; 
xliii  + 1,024  pages;  309  illustrations;  92  tables.  Price,  $5.00. 

In  the  preface  to  the  first  "edition  of  this  work,  published  in  1892,  the 
author  states: 

"Although  volumes  have  been  written  on  the  subject  of  highway 
construction,  still,  the  matter  is  widely  scattered  through  the  pages  of 


524  THE  ART  OF  ROADMAKING 

the  standard  works  on  engineering,  technical  journals,  and  periodicals, 
in  pamphlets  and   reports  of  city  engineers,   and  is,   therefore,   not 
always  easily  accessible  when  wanted.     The  author,  having  found  the 
need  of  a  comprehensive  and  practical  work  of  reference  upon  the 
many  subjects  connected  with  highways,  has  in  the  following  pages 
endeavored  to  collate  the  varied  mass  of  information." 
In  order  to  keep  abreast  of  the  times,  further  editions  of  the  book  were 
issued  in  1896  and  1900,  and  in  the  present  one,  an  extensive  revision  was 
made,  bringing  the  work  thoroughly  up  to  date. 

The  b9ok  treats  of  every  branch  of  the  subject  and  may  be  said  to  be 
cyclopedic  in  character.  The  titles  of  the  chapters  are:  Pavements, 
Materials  employed  in  the  Construction  of  Pavements,  Stone  Pavements, 
Wood  Pavements,  Asphaltum  and  Coal-Tar  Pavements,  Brick  Pavements, 
Broken-Stone  Pavements,  Miscellaneous  Pavements,  Foundations,  Resist- 
ance to  Traction,  Location  of  Country  Roads,  Width  and  Transverse  Con- 
tour, Earthwork,  Drainage  and  Culverts,  Bridges,  Retaining  Walls,  Pro- 
tection Works,  Tunnels,  Fencing,  City  Streets,  Foothpaths,  Curbs,  Gutters, 
Reconstruction  and  Improvement  of  Country  Roads,  Maintenance-Repairing, 
Cleansing,  Watering,  Trees,  Staking  Out  the  Work,  Specifications  and 
Contracts,  Implements  and  Prices,  Miscellaneous  Notes.  Four  Appendices: 
Naming  and  Numbering  Country  Roads  and  Houses;  Methods  of  Assessing 
the  Cost  of  Street  Paving;  Ordinance  Regulating  the  Width  of  Wagon- 
tires;  Cycle  Paths. 

The  treatment  of  the  various  chapters  is  quite  full  and  satisfactory. 
There  are  over  three  hundred  illustrations  and  there  is  a  remarkably  com- 
prehensive index,  covering  93  pages. 

1907.  Hirst,  Arthur  R. — Road  Pamphlets.  Wisconsin,  Geological  and 
Natural  History  Survey.  No.  1:  Earth  Roads.  No.  2:  The 
Earth  Road  Drag.  No.  3:  Stone  and  Gravel  Roads.  No.  4: 
Culverts  and  Bridges. 

These  are  popular  expositions  on  the  subjects  indicated,  and  should  be 
useful  for  their  intended  purpose  of  aiding  in  the  good  road  movement. 

1907.  Buckley,    Ernest    Robertson    (1872-         ).— Public    Roads;    Their 

Improvement  and  Maintenance. 
1907.  Eldridge,    Maurice    Owen. — Public-road    Mileage    Revenues    and 

Expenditures   in    the  United   States    in     1904.       (Government 

Bulletin.) 

Gives  statistics  by  states  and  counties  showing  the  character  and  extent 
of  public  roads,  the  expenditures  therefor  and  the  way  in  which  the  money 
is  raised,  also  contains  a  synopsis  of  the  road  laws  of  various  states  and  a 
tabular  comparison  by  states  of  the  percentage  of  improved  roads,  the  value 
of  farm  lands,  and  the  value  of  rights  of  way. 

1907.  Fletcher,  Austin  B. — The  Construction  of  Macadam  Roads.  (Gov- 
ernment Bulletin.) 

Gives  a  good  idea  of  methods  employed  in  constructing  macadam  roads, 
especially  as  carried  out  under  the  direction  of  the  Massachusetts  Highway 
Commission.  The  materials  and  appliances  used  are  described;  drainage, 
preparation  of  the  subgrade  and  the  placing  of  the  macadam  are  discussed. 
Extracts  from  specifications  used  in  various  states  are  given,  also  cost  data, 
and  drawings  of  culverts. 

1907.  Annual  Report  of  the  Commissioner  of  Highways  for  the  Year  1908. 
(Maine.) 

Reviews  the  work  of  the  year  and  gives  some  interesting  cost  data.  A 
reprint  of  the  proceedings  of  the  First  New  England  Road  Conference, 
held  in  Boston,  Nov.  23-24,  1908,  is  given. 

1907.  Patton,  W.  M.— A  Treatise  on  Civil  Engineering.  New  York. 
Second  Edition.  Cloth,  6X9  ins.;  1,672  pages;  464  illustrations 
and  diagrams.  Price,  $7.50. 

In  this  voluminous  treatise,  nearly  all  branches  of  engineering  science 
that  could  be  grouped  under  the  general  title  of  "Civil  Engineering,"  have 


BIBLIOGRAPHY  OF  ROADS  525 

been  treated.  Location  of  Highways  and  Country  Roads  has  been  covered 
in  one  chapter,  followed  by  a  chapter  on  Location  of  Lines  of  Communi- 
cation by  Topographical  Maps  and  one  on  Resistance  to  Traction  on  High- 
ways. 

1907.  Goodhue,   W.    F. — Municipal    Improvements.     A   Manual    of   the 

Methods,  Utility  and  Cost  of  Public  Improvements  for  the 
Municipal  Officer.  Third  Edition.  Cloth,  4X6  in.;  viii-!-207 
pages;  illustrated.  Price,  $1.50. 

This  book  is  intended  not  for  the  technical  reader,  but  for  the  members 
of  the  town  council  and  for  the  non-professional  reader.  There  are  30 
chapters,  of  which  two  treat  of  street  surface  and  street  grades  and  one  of 
highway  bridges. 

1908.  Leighton,  Henry. — Road  Materials  of  Southern  and  Eastern  Maine. 
1908.  Hubbard,  Prevost. — Dust  Preventives.     (Government  Bulletin.) 

This  circular  is  rather  a  summary  and  compilation  of  principles  than  a 
record  of  experimental  work. 

1908.  Page,  Logan  W. — Dust  Preventives.     (Government  Bulletin.) 
1908.  Progress  Reports  of  Experiments  with  Dust  Preventives.     (Govern- 
ment Bulletin.) 

1908.  Hill,  Gary  LeRoy. — Wood  Paving  in  the  United  States.  (Govern- 
ment Bulletin.) 

This  pamphlet  takes  up  the  progress  of  wood  paving,  the  qualities  of  -jreo- 
soted  wood  pavement,  problems  in  wood  paving,  laying  the  pavement,  inain- 
tenance  and  a  descriptive  discussion  of  an  experimental  pavement. 

1908.  Palliser,  Charles. — Modern  Cement  Sidewalk  Construction.  A 
Practical  Treatise  for  the  Workman.  New  York.  Cloth,  5X7 
ins.;  pp.  64;  illustrated.  Price,  $0.50. 

The  construction  of  cement  sidewalks,  curbs  and  gutters  is  concisely  ex- 
plained in  this  book,  directions  being  given  regarding  the  selection  and  test- 
ing of  the  cement,  sand,  stone,  gravel,  etc.,  the  special  tools  used ;  the  laying, 
finishing,  seasoning,  coloring,  etc.;  together  with  cost  data  for  a  number  of 
cases,  with  complete  specifications  for  each.  Simple  language  has  been  used 
throughout  the  book,  and  all  technical  terms  introduced  are  clearly  defined. 

1908.  Ryves,  Reginald  Arthur.— The  King's  Highway.  The  Nature, 
Purpose  and  Development  of  Roads  and  Road  Systems.  London 
and  New  York.  Cloth,  S^Xlli  ins.;  96  pages;  34  illustrations. 
Price,  $2.00,  net. 

This  book  is  largely  devoted  to  English  roads  and  in  many  ways  it  is 
quite  different  from  other  road  books.  There  are  21  comparatively  short 
chapters  dealing  with  Foreign  (outside  of  Great  Britain)  Road  Systems, 
Some  Points  of  Foreign  Practice,  Road  Administration  in  the  United 
Kingdom,  The  Departmental  Committee  of  1903,  Highway  Law,  Mechan- 
ical Power  Traction,  Width  and  Safety,  The  Road  Crust — Wearing  and 
Weathering  Roads,  Road  Lamps  and  Carriage  Lamps,  Special  Roads, 
Maintenance  and  Repair,  Road  Stones,  Testa  of  Road  Stones,  Wheels, 
Dust  and  Prevention — Tar-Macadam,  Bridges,  Climate,  and  Geology,  The 
Roadside,  Frost,  Wind  and  Snow. 

1908.  Richardson,  Clifford  (1856-         ).— The  Modern  Asphalt  Pavement. 
Second    Edition,    Revised    and    Enlarged.     New    York.     Cloth, 
ins.;  629  pages;  42  illustrations.     Price,  $3.00. 

"The  object  of  this  book  is  to  demonstrate  the  nature  of  asphalt 
pavements  and  the  causes  of  defects  in  them,  to  bring  about  improve- 
ment in  the  methods  of  their  construction,  and  to  show  how  this  can 
be  done. 

"The  conclusions  which  are  advanced  are  the  results  of  twenty 
years'  experience  in  the  industry  by  the  writer  with  pavements  in 


526  THE  ART  OF  ROADMAKING 

over  one  hundred  cities  in  the  United  States  and  several  in  England, 

Scotland,  and  France,  involving  the  construction  of  between  twenty 

and  thirty  million  yards  of  surface."  —  EXTRACT  FROM  INTRODUCTION. 

The  contents  are  divided  into  nine  parts:    The  Foundation  and   Inter- 

mediate Course:    The  Materials  Constituting  the  Asphalt  Surface  Mixture; 

Native  Bitumens  in  Use  in  the  Paving  Industry;   Technology  of  the  Paving 

Industry;     Handling  of  Binder  and   Surface  Mixture  on  the  Street;    The 

Physical    Properties    of    Asphalt    Surfaces;     Specifications    for,    and    Merits 

of  Asphalt  Pavements;  Causes  of  the  Defects  in,  and  the  Deterioration  of 

Asphalt  Surfaces;    Control  of  Work;    Appendix. 

This  is  one  of  the  recognized  standard  books  on  the  subject  of  road 
work  —  in  a  lengthy  review  of  the  first  edition  (1905)  Engineering  News 
speaks  in  most  favorable  terms  of  it  and  says:  "It  is  not  too  much  to  say 
that  Mr.  Richardson's  book  should  be  classed  with  those  which  appear 
too  infrequently,  but  whose  appearance  mark  epochs  in  the  industry  to 
which  they  relate." 

1908.  Spalding,  Frederick  Putnam  (1857-  ).  —  A  Text-book  on  Roads 
and  Pavements.  Third  Edition,  Revised  and  Enlarged.  New 
York.  Cloth,  4fX7£  ins.  340  pages;  51  illustrations.  Price, 
$2.00. 

"The  aim  of  this  work  is  to  give  a  brief  discussion,  from  an 
engineering  standpoint,  of  the  principles  involved  in  highway  work, 
and  to  outline  the  more  important  systems  of  construction  with  a 
view  to  forming  a  text  which  may  serve  as  a  basis  for  a  systematic 
study  of  the  subject."  —  EXTRACT  FROM  PREFACE. 

"While  it  is  primarily  intended  as  a  text-book  for  classes  in  engi- 
neering schools,  it  will  be  found  a  convenient  and  satisfactory  hand- 
book for  non-professional  and  general  readers  who  wish  to  inform 
themselves  in  the  elementary  principles  of  designing  and  constructing 
roads  and  pavements.  .  .  .  The  arrangement  of  subjects  and 
chapters  does  not  differ  materially  from  the  other  leading  books 
on  roads  and  pavements,  .  .  .  but  within  the  appropriate  scope  of 


a   college    text-book,    the   author   has    accomplished    all    that    could 

nably  be  demanded."  —  Engin 
Contents:      Road    Economics    and    Management;     Drainage    of    Streets 


reasonably  be  demanded."  —  Engineering  News,  Dec.  17,  1908. 


and  Roads;  Location  of  County  Roads;  Improvement  and  Maintenance 
of  Country  Roads;  Broken  Stone  Roads;  Foundation  for  Pavements; 
Brick  Pavements;  Bituminous  Pavements;  Wood-Block  Pavements; 
Stone-Block  Pavements;  City  Streets. 

1908.  Morrison,  Charles  Edward.  —  Highway  Engineering.  New  York. 
Cloth,  5|X9ins.;  315  pages;  60  illustrations.  Price,  $2.50. 

The  preface  states  that  this  book  was  prepared  as  a  text-bopk  for  second- 
year  students  in  the  Civil  Engineering  department  of  Columbia  University, 
with  a  view  to  furnishing  a  text  in  which  the  fundamentals  of  the  subject 
should  not  be  buried  in  a  mass  of  detail;  and  further  states  that  the  book 
is  not  a  reference  work,  but  rather  one  in  which  it  has  been  the  endeavor 
to  outline  and  emphasize  those  basic  principles  which  are  essential  to 
good  highways.  The  contents  cover:  Road  Resistances,  Earth  Roads, 
Gravel  Roads,  Broken-stone  Roads,  Miscellaneous  Roads,  Street  Design, 
Stone  Pavements,  Brick  Pavements,  Asphalt  Pavements,  Modern  Wooden 
Pavements. 

1908.  Brandt,  Charles  Edward  (1847-  ).  —  Road  Locating  and  Building 
Simplified.  For  Use  in  the  Common  Schools.  Boards,  5X7| 
ins.;  106  pages;  illustrated.  Price,  $1.00. 

This  book  was  written  for  use  in  the  common  schools  and  is  of  little 
practical  value  to  the  engineer.  It  contains  the  rudiments  of  road  making 
and  endeavors  to  simplify  the  art  of  road  location  and  construction  to 
the  level  of  elementary  studies  with  the  hope  of  educating  the  school  pupils 
up  to  the  good-roads  idea. 

1908.  Byrne,  Austin  T.,  and  Phillips,  Alfred  E.  —  Highway  Construction. 
A  Practical  Guide  to  Modern  Methods  of  Roadbuilding  and  the 
Development  of  Better  Ways  of  Communication.  Cloth,  6^X9f 
ins.;  136  pages;  79  illustrations  and  2  plates.  Price,  $1.00. 

This  is  an  elementary  book  consisting  mainly  of  a  brief  epitome  of 
Byrne's  cyclopedic  volume,  "A  Treatise  on  Highway  Construction." 


BIBLIOGRAPHY   OF  ROADS  527 

1908.  Boorman,  Thomas  Hugh  (1851-  ). — Asphalts:  Their  Sources 
and  Utilizations.  New  York.  Cloth,  6^X9^  ins.;  216  pages; 
48  full-page  plates.  Price,  $3.00. 

A  comprehensive  manual  in  the  asphalt  industry.  The  first  eleven 
chapters  are  devoted  to  descriptions  of  the  occurrence,  properties,  and  uses 
of  the  various  forms  of  asphaltic  substances.  Two  chapters  then  follow 
on  the  developments  of  the  asphalt  industry.  Asphaltic  oils  and  their 
application  to  roads  for  the  purpose  of  making  them  dustless  are  discussed 
in  the  succeeding  six  chapters.  There  are  then  included  chapters  dealing  with 
municipal  asphalt  plants,  asphalt  waterproofing,  asphalt  for  manufacture, 
and  a  short  chapter  on  asphalt  machinery. 

1908.  Supplement  to  Pennsylvania  Road  Laws. 

1908.  Coane,  John  M.,  Henry,  E.,  and  John  M.,  Jr.— Australasian  Roads. 
A  Treatise,  Practical  and  Scientific,  in  the  Location,  Design, 
Construction  and  Maintenance  of  Roads  and  Pavements. 
Melbourne,  Australia.  Cloth,  5£X8|  ins.;  334  pages;  13  illus- 
trations. 

The  title  of  this  book  is  somewhat  misleading.  Instead  of  being  a  treatise 
on  the  method  of  road  building  in  Australia,  as  one  might  expect  from 
the  title,  it  is  a  compilation  of  data  on  the  best  practice  in  road  engineer- 
ing in  other  countries  for  the  guidance  of  Australasians. 

1908.  Judson,  William  Pierson  (1849-  ).— Road  Preservation  and 
Dust  Prevention.  New  York.  Cloth,  5|X8f  ins.;  146  pages; 
illustrated.  Price,  SI. 50,  net. 

Mr.  Judson  has  rendered  the  road  engineers  and  the  road  makers  of  the 
country  a  valuable  service  in  collecting  and  sifting  the  great  mass  of  data 
on  the  subject  of  dust  prevention  scattered  through  periodicals  and  society 
transactions  and  in  reducing  this  material  to  a  condition  that  permits  of 
comparisons  being  made,  giving  officials  who  are  not  experts  reliable, 
information  to  guide  them  in  the  selection  of  a  suitable  remedy  for  the 
cure  of  their  own  local  troubles. 

The  opening  chapter  treats  of  the  origin  of  road  dust  and  its  economic 
value  in  the  preservation  of  the  road  surface.  The  other  eight  chapters 
deal  with  the  various  means  of  treatment  and  construction  with  a  view 
toward  dust  prevention,  taking  up,  respectively,  Moisture,  Oil  Emulsions, 
Oils,  Coal-tar  Preparations,  Tar-spraying  Machines,  Tar-macadam,  Rock- 
Asphalt,  Macadam  and  Bitulithic  Pavement.  Each  chapter  describes  the 
general  process,  its  variations  and  details  of  experiments,  giving  methods 
of  use,  results,  costs,  a  .id  a  summary  of  conclusions  arrived  at  based  on  a 
consideration  of  the  details  of  many  experiments.  The  comparative  values 
of  the  various  methods  and  their  suitability  for  local  conditions  as  brought 
out,  will  enable  road  builders  to  profit  by  the  experience  of  others  and 
thus  save  much  of  the  cost  of  experimenting  for  themselves. 

1908.  The  Control  of  Street  Openings.  A  Discussion  Concerning  an  Ulti- 
mate Remedy  for  the  Destruction  of  City  Pavements  by  Openings. 

1908.  Baker,  Ira  0. — A  Treatise  on  Roads  and  Pavements.  New  York. 
New  Printing  of  1903  Edition.  Cloth,  6X9  ins.;  655  pages; 
65  tables;  171  illustrations.  Price,  $5.00. 

Consists  of  two  parts:  I. — Country  Roads,  including  matters  relating 
to  earth,  gravel  and  broken-stone  roads  in  rural  districts;  II. — Street 
Pavements.  The  reason  for  this  division  is  given  in  the  introduction: 

"The  problems  involved  in  the  construction  and  maintenance  of  rural 
highways  differ  materially  from  those  which  are  encountered  in  the  improve- 
ment and  care  of  city  streets  ...  In  each  division  of  the  subject  certain 
general  principles  will  first  be  considered,  and  the  further  discussion  will 
be  divided  according  to  the  several  materials  in  use  for  the  road  surface.  .  .  . 

In  a  review  in  Engineering  News  (February  19,  1903)  the  merits  and 
limitations  of  this  book  were  compared  in  detail  with  those  of  the  various 
other  works  on  the  subject,  and  the  conclusions  reached  were  summarized 
in  one  paragraph: 


528  THE  ART   OF  ROADMAKING 

"Having  considered  the  whole  treatise  somewhat  in  detail,  we  may 
say  that  as  a  text-book  for  students  this  new  work  is  superior  to  Byrne, 
but  partly  because  it  is  more  recent.  It  is  also  superior  to  Tillson,  but 
chiefly  because  it  is  more  comprehensive.  Tillson  wrote  with  a  much 
wider  experience  than  has  any  other  author  of  a  manual  on  pavements, 
but  he  held  himself  closely  to  that  subject,  even  to  the  exclusion  of 
sidewalks.  This  limitation  13  commendatory,  but  must  be  borne  in  mind 
when  assigning  Tillson  a  place  among  other  treatises  on  road  and  street 
work.  But  when  we  look  at  Baker's  work  from  the  viewpoint  of  the 
engineer  already  possessed  of  most  of  the  American  works  above  men- 
tioned, we  find  very  little  that  is  not  to  be  found  in  them  and  in  recent 
current  literature.  The  author  has  compiled  with  excellent  judgment, 
but  excepting  some  original  data  on  traction,  voids  in  sand  and  stone, 
and  analyses  of  certain  gravels,  we  find  no  real  contribution  to  the  stock 
of  engineering  knowledge  of  roads  and  pavements." 

1908.  King,  David  W. — The  Use  of  the  Split-log  Drag  on  Earth  Roads. 
(Government  Bulletin.) 

1908.  McCullough,  Ernest. — Engineering  Work  in  Towns  and  Small 
Cities.  Second  Edition.  Chicago.  Cloth,  4|X7|ins.;  510 
pages;  illustrations  and  tables.  Price,  $3.00,  net. 

In  the  introductory  chapter  the  author  writes: 

"This  book  is  written  for  two  classes  of  officials  in  towns  and  cities 
having  a  population  of  less  than  20,000  inhabitants,  and  it  may  be 
found  useful  in  some  larger  places. 

"Elected  officials  and  those  who  have  no  technical  education 
belong  to  the  first  class.  They  come  into  intimate  relatipns  with 
men  who  have  charge  of  engineering  work,  are  interested  in  it,  often- 
times direct  it,  and  therefore  may  be  benefited  by  reading  this 
book. 

"The  second  class  is  composed  of  engineers  and  surveyor?  holding 
the  position  of  town  or  city  engineer,  especially  those  with  little 
or  no  previous  experience  in  municipal  engineering." 

Three  chapters  (100  pages)  are  devoted  to  Roads  and  Streets; 
Walks,  Curbs,  and  Gutters;  Street  Pavements. 

1908.  Aitkin,  Thomas. — Roadmaking  and  Maintenance.  A  Practical 
Treatise  for  Engineers,  Surveyors  and  Others.  With  an  His- 
torical Sketch  of  Ancient  and  Modern  Practice.  Second  Edition. 
London.  Cloth,  6 X9|  ins.;  525  pages;  167  illustrations.  Price, 
21s.;  American,  $6.00,  net. 

This  is  a  British  book,  but  its  recognized  usefulness  h~s  made  it  a 
standard  work  in  America  as  well  as  in  England.  The  results  of  a  wide 
experience  are  set  down  in  a  clear  and  orderly  fashion,  supplemented  by 
well-chosen  illustrations. 

The  contents  are  divided  into  two  parts:  (1)  Macadamized  Roads  and 
(2)  Carriageways  and  Footpaths.  The  title"}  of  the  chapters  are:  Part  I. 
—Road-Making  and  Maintenance — Historical  Sketch;  Resistance  to  Trac- 
tion— Wheels  and  Weights  on  Them;  Laying  Out  New  Roads  and  the 
Improvement  of  Existing  Lines  of  Communication;  Earthwork,  Drainage, 
Retaining  Walls,  Culverts,  Bridges  and  Protection  of  Roads;  Road-Making 
Materials;  Quarrying;  Stone-Breaking  and  Haulage;  Road-Rolling  and 
Scarifying;  The  Construction  of  New  and  the  Maintenance  of  Existing 
Roads-  The  Prevention  of  Dust.  Part  II. — Carriageways  and  Footways — 
Preliminary  Remarks — Foundations  and  Pitched  Pavements;  Wood 
Pavements;  Asphalt  Pavements;  Brick  Pavements  for  Carriageways; 
Tar  Macadam;  Conclusions;  Footways-Paving  Materials  for  Footpaths, 
Curbs,  Channels,  Gutters;  Testing  the  Surfaces  of  Carriageways;  Subways. 

The  first  edition  of  Mr.  Aitkm's  book  was  brought  out  in  1900  and  was 
very  favorably  received.  It  appeared  at  a  time  when  the  art  of  road- 
making  had  not  advanced  to  as  high  a  state  of  perfection  in  this  country 
as  in  Great  Britain,  and  it  was  particularly  useful  as  recognizing  the  value 
and  describing  the  methods  of  substituting  machine  for  hand  labor  in  both 
construction  and  maintenance.  It  also  gave  detailed  figures  of  cost  and, 
while  these  are,  of  course,  of  far  less  use  in  this  country  than  in  England, 
owing  to  the  variation  in  local  conditions  and  in  currency  systems,  the 
fact  that  many  of  these  were  inserted  to  show  the  relative  advantages  of 
different  methods,  make  them  of  some  interest  to  American  engineers. 
The  present  edition  has  been  thoroughly  revised.  The  greater  part  of  the 


BIBLIOGRAPHY  OF  ROADS  529 

volume  relates  to  the  construtcion  of  macadam  and   like  roads,   but  the 
various  kinds  of  city  pavements  are  also  considered. 

In  an  Appendix  of  50  pages  is  given  the  full  text  of  a  report  on  "The 
Resistance  of  Road  Vehicles  to  Traction,"  made  to  the  British  Association 
for  the  Advancement  of  Science,  by  a  committee  of  which  the  author  was 
a  member. 

1909.  Judson,  William  Pierson  (1849-  ). — City  Roads  and  Pavements. 
Suited  to  Cities  of  Moderate  Size.  Fourth  Edition,  Revised. 
New  York.  Cloth,  5|X8fins.;  197  pages;  69  illustrations. 
Price,  $2.00,  net. 

This  book  deals  especially  with  the  many  varieties  of  hard-surfaced 
roads,  and  has  for  a  number  of  years  been  considered  a  standard  guide 
to  the  building  of  rural  highway  and  town  streets,  as  well  as  of  city  pave- 
ments. 

Some  interesting  historical  matter  in  early  stone  wheel  tracks  in  America 
are  given;  also  tables  for  determining  standard  crowns,  giving  the  cost 
of  asphalt  pavement?,  grades  and  costs  of  different  kinds  of  pavements 
and  other  valuable  information  of  like  character. 

The  titles  of  the  chapters  are:  Preparation  of  Streets  for  Pavements; 
Ancient  Pavements;  Modern  Pavements;  Concrete  Base  for  Pavement; 
Stone-Block  Pavements;  Concrete  Pavements;  Wood  Pavements;  Iron- 
Slag  Block  Pavements;  Vitrified-Brick  Pavements;  American  Sheet- 
Asphalt,  Artificial  and  Natural;  Bitulithic  Pavement;  Broken  Stone  Roads. 

1909.  Smith,  J.  Walker. — Dustless  Roads.  Tar  Macadam.  A  Practical 
Treatise  for  Engineers,  Surveyors  and  others.  London.  Cloth, 
6X9  ins.;  225  pages;  24  illustrations.  Price,  S3. 50,  net. 

This  book  is  based  largely  upon  a  long  continued  intimate  personal 
experience  in  dealing  with  the  subject  of  tar  macadam. 

Over  thirty  pages  are  devoted  to  the  production  and  refinement  of  tar. 
The  standardization  of  the  matrix  and  associated  tests,  the  aggregate,  the 
different  methods  of  preparing  and  laying  tar  macadam  (four  chapters), 
and  mechanical  mixing  are  then  taken  up  and  later  in  the  book  the  effects 
of  wear,  porosity,  density,  and  distribution  of  weight,  scavenging  or  road 
cleansing,  watering,  and  maintenance  generally;  camber  or  crown,  grade, 
noiselessness,  and  hygienic  advantages  and  wearing  and  tractive  effort  are 
considered. 

The  final  chapter,  entitled  "Tar  Spraying  or  Spreading  Ordinary  Macadam 
Surfaces,"  contains  considerable  information  on  tar  spraying,  as  well  as 
interesting  but  brief  history  of  the  practice.  An  appendix  gives  in  tabulated 
form  replies  received  to  inquiries  regarding  "tar  macadam  and  the  tarring 
of  macadam  surfaces,"  made  by  various  British  municipal  engineers.  These 
returns  are  also  drawn  upon  by  the  author  from  time  to  time  throughout 
a  large  part  of  his  text,  thus  supplementing  his  own  experience  and  ideas 
with  those  of  others. 

1909.  Vinsonneau,  Jules. — Le  Route  Moderne. — Paris. 
1909.  Harris,  G.  Montagu. — The  First  International  Road  Congress,  Paris, 
1908.     London.     Cloth,  6X9  ins.;    140  pages;   Price,  $1.50. 

1909.  Thomson,  Sanford  E. — Concrete  in  Highway  Construction.     $1.00. 

1910.  Frost,  Harwood. — The  Art  of  Roadmaking.     New  York.     Cloth, 

6X9  ins.;  544  pages;  260  illustrations.     Price,  $3.00,  net. 

An  explanation  of  the  problems  involved  in  the  building  of  roads,  the 
various  roadmaking  materials,  qualities  of  roads  suited  for  various  purposes, 
ind  other  information  written  in  a  style  suitable  for  the  general  reader. 

EARTHWORK  AND   ROCK  EXCAVATION 

Allen,  C.  F. — Tables  for  Earthwork  Computation.     $1.50. 
Baker,  B. — Lateral  Pressure  Earthwork.     $0.50. 
Crandall,  C.   L.— Railway  and    Other    Earthwork  Tables.     Third 
Edition.     $1.50. 


530  THE  ART  OF  ROADMAKING 

Crockett,   C.  W.— Methods  for  Earthwork  Computations.     $1.50. 
Cunningham,  D.  W. — Earthwork  Tables.     $4.25. 
Gillette,  H.  P.— Rock  Excavation,  Methods  and  Cost.     1904.   $3.00. 
1903.  Gillette,    H.    P.— Earthwork    and    Its    Cost.     New    York.     Cloth, 

5X8  ins.;    244  pages;    tables,   folding  plates  and   illustrations. 

Price,  $2.00,  net. 

There  are  17  chapters  treating  of:  The  Art  of  Cost  Estimating;  Earth 
Shrinkage;  Earth  Classification  and  Cost  Data  for  all  kinds  of  work  in 
connection  with  excavating,  grading,  dredging,  digging,  rilling,  etc. 

1905.  Gillette,  H.  P. — Handbook  of  Cost  Data  for  Contractors  and  Engi- 
neers. A  Reference  Book  giving  Methods  of  Construction  and 
Actual  Costs  of  Materials  and  Labor  on  Numerous  Engineering 
Works.  Chicago.  Morocco,  4^X6|  ins.;  610  pages;  30  illus- 
trations and  many  tables.  Price,  $4.00,  net.  (See  page  533.) 

As  explained  by  the  title,  this  book  is  a  record  of  costs  of  actual  work. 
It  deals  with  many  classes  of  engineering  practice,  one  section  (Sec.  II.) 
being  devoted  to  "Cost  of  Earth  Excavation";  one  (Sec.  III.)  to  "Cost 
of  Rock  Excavation,  Quarrying,  and  Crushing,"  and  one  (Sec.  IV.)  to 
"Cost  of  Roads,  Pavements,  Walks,"  etc.  Macadam  and  telford  roads, 
the  various  kinds  of  pavements,  curbs,  gutters,  and  walks  are  discussed 
and  their  detail  costs  set  forth.  The  first  two  sections  are  principally  a 
synopsis  and  condensation  of  the  author's  books;  "Earthwork  and  Its 
Cost"  and  "Rock  Excavation — Methods  and  Cost,"  both  of  which  are 
elsewhere  noticed. 

1907.  Henderson,  R.  S. — Earthwork  Tables.  New  York.  Heavy  paper; 
oblong;  32  pages.  Price,  $1.00,  net. 

Divided  into  two  parts: 

Part  I. — Preliminary  Earthwork  Tables,  giving  cubic  yards  per  100  feet 
for  level  sections,  to  which  is  added  a  graphical  method  of  estimating 
quantities  from  a  profile. 

Part  II. — Earthwork  Tables,  giving  the  volume  in  cubic  yards  of  pris- 
moids  100  feet  long  by  the  average  and  area  method. 

This  is  a  very  useful  book  of  tables;  exceptionally  complete,  wide  in  range 
and  compact  in  arrangement. 

Grace's  Earthwork  Tables  for  Calculating  the  Cubical  Contents 
of  Cuttings.  1908.  $5.00. 

Housden,  C.  E.— Practical  Earthwork  Tables.     1907.     $0.90. 

Howard,  C.  R. — Earthwork  Mensuration.     $1.50. 

Hudson,  J.  R. — Tables  for  Calculating  Cubic  Contents  of  Excava- 
tions, etc.  $1.00. 

Morris,  E. — Easy  Rules  for  Measurement  of  Earthwork.     $1.50. 

Prelim,  C.— Earth  and  Rock  Excavation.     1904.     $3.00. 

Taylor,  T.  U.— Prismoidal  Formulas  and  Earthwork.     $1.50. 

Trautwine,  J.  C. — Method  of  Calculating  Cubic  Contents  of  Excava- 
tions and  Embankments  by  Diagrams.  Ninth  Edition.  $2.00. 

Warner,  J. — New  Theorems,  Tables,  and  Diagrams  for  Computation 
of  Earthwork.  $4.00. 

BLASTING  AND   EXPLOSIVES 

Andre,  G.  G.— Rock  Blasting.     $3.00. 
Berthelot,  M.— Explosives  and  Their  Power.     $9.60. 
Daw,  A.  W.,  and  Z.  W.— Principles  of  Rock  Blasting.     Part  I. 
$6.00. 


BIBLIOGRAPHY  OF  ROADS  531 

Eissler,  M. — Hand-book  on  Modern  Explosives.     $5.00. 

— . — Modern  High  Explosives.     Third  Edition.     $4.00. 
Foster,  J.  G. — Submarine  Blasting  in  Boston  Harbor.     $3.50. 
Guttman,  0.— Blasting.     $3.00. 

Maurice,  W. — Electric  Blasting  Apparatus  and  Explosives.     $3.50. 
Sanford,  P.  G.— Nitro-Explosives.     $3.00. 

CULVERTS   AND   DRAINS 

Chamberlain,  W.  I.— Tile  Drainage.     $0.35. 

Dempsey,  G.  D. — Drainage  of  Lands,  Towns,  etc.     $1.80. 

Jones,  E.  R. — Notes  on  Drainage.     $1.00. 

Klippart,  J.  H. — Principles  and  Practice  of  Land  Drainage.     $1.00. 

Marston,  A. — Sewers  and  Drains.     $1.00. 

Miles,  M.— Land  Draining.     $1.00. 

Scott,  J. — Draining  and  Embankment.     $0.60. 

Waring,  G.  E.— Drainage  for  Profit  and  Health.     $1.00. 

HIGHWAY   BRIDGES 

Boiler,  A.  P. — Construction  of  Iron  Highway  Bridges.     $2.00. 

1721.  Gautier,  Hubert  (1660-1737).— Traite  de  la  Construction  des 
Chemins. 

1850.  Geddse,  George. — Observations  on  Plank  Roads. 

1899.  Report  on  the  Highways  of  Maryland. 

1901.  Cooper,  T. — General  Specifications  for  Foundations  and  Substruc- 
tures of  Highway  and  Electric  Railway  Bridges.  $1.00. 

1901.  Law,  Henry. — The  Construction  of  Roads  and  Streets.  Sixth 
Edition. 

1904.  Fowler,  C.  E. — Ordinary  Foundations.     $3.50. 

n.  d.  Osborn  Engineering  Co.  General  Specifications  for  Highway  Bridge 
Superstructures.  $0.25. 

n.  d.    Thacher,  E. — General  Specifications  for  Highway  Bridges.     $0.25. 

1906.  Buel,  Albert  W. — General  Specifications  for  Steel  Railroad  Bridges 
and  Structures,  with  a  section  making  them  applicable  to  High- 
way Bridges  and  Buildings.  $0.50. 

1908.  Watson,  W.  J. — General  Specifications  for  Concrete  Bridges.    $1.00. 

1908.  Ketchum,  Milo  S.— The  Design  of  Highway  Bridges  and  the  Calcu- 
lation of  Stresses  in  Bridge  Trusses.  New  York  and  London. 
Cloth,  6X9  ins;  xxi  +  554  pages;  309  illustrations;  77  tables. 
$4.00,  net. 

"The  aim  in  writing  this  book  has  been  to  give  a  brief  course  in  the 
calculation  of  the  stresses  in  bridge  trusses,  followed  by  a  systematic  dis- 
cussion of  the  details  and  design  of  highway  bridges. 

"\Vhile  there  are  many  excellent  books  in  which  the  different  types 
of  railway  bridges  are  discussed  in  detail,  little  attention  has  heretofore 
been  given  to  the  design  of  highway  bridges.  As  a  consequence  of  this 
neglect,  many  of  our  highway  bridges  have  been  very  badly  designed; 
the  design  of  these  structures  being  ordinarily  left  to  an  engineer  without 
experience,  or  to  the  agent  of  some  bridge  company,  who  is  more  interested 


532  THE  ART  OF  ROADMAKING 

in  the  resulting  profits  than  in  obtaining  a  good  design.  The  calculation 
of  the  stresses  in  highway  and  railway  bridges  are  similar,  but  the  problems 
in  the  design  of  the  two  types  are  very  different,  due  to  the  different  require- 
ments and  conditions. 

"In  the  course  of  the  calculation  of  stresses,  both  the  algebraic  and  the 
graphic  methods  of  calculating  stresses  in  bridge  trusses  are  described 
in  detail." — EXTRACT  FROM  PREFACE. 

The  above  extract  from  the  Preface  will  give  a  general  idea  of  the  nature 
of  the  book.  It  was  primarily  written  for  the  purposes  of  a  text-book 
for  engineering  schools,  but,  on  the  other  hand,  it  is  also  intended  to  meet 
the  needs  of  municipal  and  county  engineers,  surveyors,  and  all  men 
engaged  in  highway  bridge  construction,  whose  duties  require  a  knowledge 
of  design  and  construction,  and  as  the  first  book  on  the  specific  subject 
of  highway  bridges  that  has  been  published  for  some  time,  it  is  deserving 
of  the  most  careful  consideration. 

The  contents  are  divided  into  three  parts:  Stresses  in  Steel  Bridges; 
The  Design  of  Highway  Bridges;  and  a  Problem  in  Highway  Bridge 
Details.  Part  I.  deals  with  Types  of  Steel  Bridges;  Loads  and  Weight? 
of  Highway  Bridges;  Methods  for  the  Calculation  of  Stresses  in  Framed 
Structures;  Stresses  in  Beams;  Stresses  in  Highway  Bridge  Trusses; 
Stresses  in  Railway  Bridge  Trusses;  Stresses  in  Lateral  Systems;  Stresses 
in  Pins;  Eccentric  and  Combined  Stresses;  Deflection  of  Trusses;  Stresses 
in  Rollers  and  Camber;  the  Solution  of  Problems  in  the  Calculation  of 
Stresses  in  Bridge  Trusses.  Part  II.  takes  up  Short  Span  Steel  Highway 
Bridges;  High  Truss  Steel  Highway  Bridges;  Plate  Girder  Bridges;  Design 
of  Truss  Members;  The  Details  of  Highway  Bridge  Members;  The  Design 
of  Abutments  and  Piers;  Stresses  in  Solid  Masonry  Arches;  Design  of 
Masonry  Bridges  and  Culverts;  The  Design  of  Timber  and  Combination 
Bridges;  Erection,  Estimates  of  Weight  and  Cost  of  Highway  Bridges; 
General  Principles  of  Design  of  Highway  Bridges.  Part  III.  discusses  in 
detail  the  design  of  a  160-ft.  Pratt  truss  span. 

1909.  Tyrell,  H.  S. — The  Longest  Simple-Truss  Span  Highway  Bridge. 
Paper,  6X9  ins.;    22  pages,  15  diagrams,  and  1  half-tone  view. 

Price,  50  cents. 

This  pamphlet  describes  the  highway  bridge  over  the  Miami  River  at 
Elizabethtown,  Ohio,  which  is  remarkable  as  being  the  longest  simple- 
truss  span  in  existence. 

FORESTRY 

Brown,  J.  P.— Practical  Arboriculture,  1906.     $2.50. 

Bruncken,  E. — North  American  Forests  and  Forestry.     $2.00. 

Fernow,  B.  E. — Economics  of  Forestry.     $1.50. 

Fuller,  A.  S.— Practical  Forestry.     $1.50. 

Gifford,  J. — Practical  Forestry  for  Beginners.     $1.20. 

Hough,  F.  B.— Elements  of  Forestry.     $.1.50 

Hough,  R.  B. — American  Woods.     Each  part,  $5.00. 

Houston,  E.  J.— Outlines  of  Forestry.     $1.00. 

Nisbet,  J.— Studies  in  Forestry.     $2.00. 

Roth,  F.— First  Book  of  Forestry.     $1.20. 

Schwartz,  G.  F. — Forest  Trees  and  Forest  Scenery.     $1.50. 

Schlich,  W.— Manual  of  Forestry.     5  vols.     $17.20. 

Springer,  J.  S.— Forest  Life  and  Forest  Trees.     $1.50. 

Typical  Forest  Trees.     3  ser.     $1.00.     Each,  $0.40. 

Unwin,  A.  H.— Future  Forest  Trees,  1906.     $2.25. 

TUNNELING 

While  this  branch  of  engineering  is  not  necessarily  connected  with 
the  work  of  the  municipal  engineer  and  road  builder,  a  knowledge  of 
tunnel  practice  is  useful. 


BIBLIOGRAPHY  OF   ROADS  533 

1905.  Prelini,  Charles. — Tunneling:  A  Practical  Treatise.     New  York  and 

London.     Cloth,  6X9  ins.;    326  pages;    150  illus.     Price,  $3.00. 

The  general  purpose  of  this  book  is  to  explain  all  the  operations  that 
are  required  in  tunneling  and  to  illustrate  by  suitable  examples  the  actual 
application  of  these  methods  in  practice. 

1906.  Stauffer,    David   McN. — Modern   Tunnel    Practice.     Illustrated    by 

Examples  taken  from  Actual  Recent  Work  in  the  United  States 
and  in  Foreign  Countries.  New  York.  Buckram,  6X9  ins.; 
322  pages;  138  illustrations.  Price,  $3.50,  net. 

The  material  used  in  this  book  is  taken  largely  from  the  detailed 
descriptions  of  modern  tunnel  work  found  in  the  pages  of  technical  journals, 
personal  notes  and  in  the  proceedings  of  engineering  societies,  supplemented  by 
the  experience  of  many  engineers  and  contractors.  In  every  case  the  descrip- 
tion of  any  especial  method  is  prefaced  by  a  brief  statement  of  the  physical 
conditions  which  called  for  some  particular  treatment.  The  composition, 
nature,  and  use  of  modern  explosives  have  been  treated  at  considerable 
length.  An  important  feature  is  a  glossary  of  all  the  technical  and  some 
of  the  more  unusual  terms  used  in  tunnel  work. 

1910.  Gillette,  H.  P. — Handbook  of  Cost  Data  for  Engineers  and  Con- 
tractors. Second  Edition.  Chicago.  Morocco,  4£X6f  ins.; 
1854  pages;  illustrated.  Price,  $5.00,  net. 


INDEX 


Abutments  for  bridges 

Adaptability  of  pavements 

Administration  of  highways. . . 
Advantages,  asphalt  pavements 

coal-tar  pavements 

concrete  pavement 

good  roads 

paved  city  streets 

straight  and  curved  roads  .  . 

wood  block  pavement 

American  systems  of  road  man- 
agement   

Aneroid  barometer 

Angle  of  internal  friction 

Angles  for  laying  wood  block 

pavement 

Anglesea,  improvement  in  old 

road 

Application  of  new  materials  to 

roads 

Area  of  streets 

Artificial  granite  blocks 

paving  stones 

sheet  asphalt  pavement 

stone  sidewalks 

Ascent,  curves  on 

Asphalt,  definition 

pavements 

appliances 

rock 

Asphalt-block  pavement. . 
Automobile  traffic,  effects  of, 

219, 
Autumn  works  on  roads 


B 


Balancing  earth  work 

Basalt 

Batter,  mountain  roads 


83 

34 

23 

361 

378 

381 

19 

20 

39 

340 

24 
43 
55 

352 


207 
304 
455 
460 
361 
428 
49 
357 
357 
369 
243 
376 

491 
215 


54 

113 
196 


PAGE 

Belgian  block  pavement 315 

Bench-marks 43 

Benefits  of  improvements 204 

Bibliography 505 

Binding  macadam  roads 173 

Bitulithic  pavement 244 

Bitumen 357 

Blocks,  size  of 297 

Borrow,  specifications 273 

Breaking  stone 179 

Brick  clays 325 

pavements 323 

sidewalks 426 

Bricks  for  country  roads 333 

paving,  size  and  shape 327 

Bridge  sites 49 

trusses 71 

Bridges 69 

Broken  stone  roads 154 

advantages  and  defects. ..  163 

difference  in  construction .  164 

errors  in  construction ....  165 

essentials  to  success 164 

specifications 276,  284 

Buck  scrapers 141 

Burnt  clay  roads 133 


Calcium  chloride  for  dust  pre- 
vention    227 

Calculation   of  load  on   gradi- 
ent   16 

tractive  force 12 

California  crude  petroleum 230 

Carts  for  distributing  stone  ...  181 

Catch  basins,  specifications ....  279 

Causes  destruction  of  roads  ...  93 

making  repairs  necessary  ...  212 

tractive  resistance 10 

Cement  sidewalks 430 

535 


536 


INDEX 


Cementing    action    of    broken 

stone,  theory  of 176 

value  of  stones 100 

Center  walks 307 

Characteristics  of  country 41 

Charcoal  roads 457 

"Checkerboard"  plan  of  loca- 
tion of  streets 299 

Chemical  agencies  of  road  de- 
struction       95 

City  pavements,  maintenance .     26 

materials  employed 34 

methods  of  payment 22 

opening  for  pipes 27 

questions  affecting  design .     22 

City  streets,  cleaning 401 

design  of 296 

paved,  advantages  of 20 

use  of 407 

City  wastes,  varieties. 412 

Classification,  earth  work 53 

highway  bridges 71 

rocks 101 

Clay 115 

for  brick  making 325 

region  of  production 325 

roads 126 

improvements  of 204 

Cleaning  city  streets 401 

Clearing  roadsides 215 

country  roads,  tools 137 

Clinker  roads 459 

Coal-slack  roads 457 

Coal-tar  pavements 377 

tests  of 235 

use  for  dust  prevention 231 

Cobblestone  gutters,  specifica- 
tions    280 

pavement 313 

Commission,  state-aid 251 

Comparative  values  of  various 

pavements 31 

Compass 43 

"Concentric"  plan  of  location 

of  streets 301 

Concrete  bridges 79 

cubes j 399 

foundations. . .  : 399 

pavements 380 

sidewalks..  .   430 


Concrete-block  trackways 

Concreting  curbs 

Conglomerate.  metamorphic 

rock 

Connecticut,  construction  of 
state  roads 

county  highway  commis- 
sioners  

how  to  get  state  aid 

maintenance  of  state  aid 
highways 

payment  for  state  aid  high- 
ways  

powers  of  counties 

specifications  for  state  aid 
roads 

state  aid  fund 

state  aid  highways 

state  highway  department .  . 
Construction,  asphalt  pave- 
ments  

brick  pavements 

broken  stone  roads. 

concrete  pavements 

earth  roads 

gravel  roads 

state  aid  roads 

specifications 

state  roads 

works 

Contour  lines 

Contractor's  guarantee.  ...  26, 

Contracts 

Control  of  road  dust 

Convict  labor 

Co-operation  in  street  cleaning . 

Copper  slag  roads 

Corduroy  roads 

on  mountains 

Cork  pavements 

Cost,  burnt  clay  roads 

concrete  pavements 

earth  work 

macadam  surface 

maintenance 

pavements 

sand  clay  roads 

transportation 

wood  block  pavements 

County  highway  commissioners 


PAGE 

452 

446 

105 
266 

263 
264 

271 

269 
261 

288 
259 
257 
254 

365 
329 
164 
388 
118 
125 
250 
272 
265 

53 

43 
487 
473 
218 
271 
411 
460 
456 
201 
459 
137 
381 

61 
185 
209 

36 
132 

21 
341 
262 


INDEX 


537 


Country  roads,  advantages  of  .  19 

brick 333 

improvement    and    mainte- 
nance    203 

location 37 

maintenance 25 

materials  employed 34 

Creo-resinate  process 349 

Creosote  oil 346 

Creosoting 345 

Crossing  stones 449 

Crown  of  road  surface 67 

Crushing  plants 181 

Culverts 81 

earth  roads 121 

specifications 274 

Curbs 424,  444 

Curved  roads,  advantages 39 

length 37 

Curves 48 

mountain  roads 200 

Cushion,  wood  block  pavement  349 

D 

Defects  of  existing  roads 203 

of  broken-stone  roads 149 

Design  of  city  streets 296 

Desirability  of  pavements 34 

Destructor  concrete  roads 459 

"  Diagonal "  plan  of  location  of 

streets 301 

Digest  of  state  aid  laws 252 

Dimensions  of  curbstones 444 

Diorite 112 

Disadvantages,    asphalt   pave- 
ments   361 

coal-tar  pavements 378 

wood  block  pavement 340 

Disposal  of  street  dirt 421 

Distance,  value  of  saving 45 

Distribution  of  state  aid  funds .  249 

District  highway  commissioners  262 
Disturbing      forces      affecting 

curbs 444 

Drag  scrapers 140 

Dragging  earth  roads 145 

Drainage 62 

city  streets 299 

concrete  sidewalks,   founda- 
tion..                               .  433 


Drainage,  curbs 444 

earth  roads 119 

mountain  roads 19."> 

retaining  walls 89 

Draining  tools 137 

Driving    in    middle    of    road, 

effects  of 306 

Dump  cars 144 

wagons 144 

Durability,  asphalt  pavements .  364 

brick  pavements 331 

granite  blocks 321 

pavements 36 

stones 99 

wood  block  pavement 341 

"  Durax  "  roads 461 

Dust  prevention 218 

E 

Earth  road  drag 145 

Earth  roads 117 

Earthwork 53 

specifications 272 

Economy,  bridges 87 

location 39 

road  improvements 21 

Elevating  graders 142 

Embankments 55,  58 

Errors  in  maintenance 209 

Equalizing  earthwork 54 

European  asphalt  pavements. .  360 

systems    of    road    manage- 
ment   24 

Excavation I  55 

Expansion  joints,  wood  block 

pavement 353 

Experiments,  dust  prevention .  225 

tractive  resistance 12,  14 

F 

Failures,  asphalt  pavements...  372 

concrete  sidewalks 433 

sand  clay  roads 12"8 

Fences }•>:; 

Filler,  brick  pavements 331 

joints  of  wood  pavement  .  .  .  354 

Final  grade,  establishing 48 

selection  of  route 51 

Finishing,  concrete  pavements .  396 

Firing  burnt  clay  roads 136 


538 


INDEX 


PAGE 

First  course,  macadam  roads. .  170 

Floor  beams  for  bridges 83 

Flushing  streets 420 

Foundations 62 

concrete 399 

concrete  sidewalks 435 

stone  block  pavement 318 

wood  block  pavement 349 

Fuel  for  burnt  clay  roads 135 

Funds  for  state  aid  purposes . . .  248 

G 

"  Gladwell "  system 241 

Government  tests  of  rocks  ....    116 

Grades 15,  45 

final 48 

maximum 46 

method  of  expressing 18 

method  of  overcoming 46 

minimum 48 

most  advantageous 47 

mountain  road 191 

Grading  tools 137,  145 

Granite Ill 

block 455 

pavement 316 

sidewalks 426 

Gravel 115,  123 

paths 428 

roads 123 

Gravity,  effect  on  roads 94 

Guarantees,  pavement 487 

Guard  rail,  specifications 278 

Gumbo  clay... 133 

Gutters 424,  444,  448 

cobblestone,  specifications  .  .  280 
Gyratory  crushers 179 


II 


Hand  level 43 

Hardness  of  stones 96 

Hassam  pavement 389 

Hauling  power  of  horses 16 

Heat,  effects  on  roads 94 

Hedges 463 

High  truss  bridges 77 

Highway  administration 23 

bridges 69 


Highway  commissioners,  coun- 
ty   262 

Historical  sketch  of  road  de- 
velopment   1 

Horses,  hauling  power 16 

How  localities  get  state  aid ...  264 


Ideal  pavement 29 

Igneous  rocks 102 

Improvement  of  country  roads  203 
Inclines,  arrangement  of  stone 

blocks 321 

India  rubber  pavements 460 

Instructions,  dragging  roads  .  .  151 

roadmen 213 

Instruments  used  in  location  .  .  43 

Intersections,  specifications  . .  .  290 


Jarrah.  use  in  paving 337 

Joint  filling,  stone  block  pave- 
ment   319 

Joints,  concrete  sidewalks 437 

K 

Karri,  use  in  paving 337 

Kreodone-creosote  processs  .  . .  348 


Labor  tax  system 25 

Laws  of  states  regarding  control 

of  roads 251 

Ledge    excavation,     specifica- 
tions    273 

Leg  bridge 75 

Length  of  straight  and  curved 

roads 37 

Levels 43 

Limestone 114 

Loads  drawn  by  horses  on  gra- 
dients       17 

Location,  bridges 49,  69 

country  roads 37 

economy  in 39 

mountain  roads 194 

streets 299 

Low  truss  bridges 77 


INDEX 


539 


M 

Macadam,  John  Loud  on 156 

method  of 161 

compared  with  Telford's  154 

defects 163 

Macadam,  essential  qualities  ..      96 

roads,  construction  of 169 

cost  of 185 

dimensions  of  surface 168 

specifications 281,  284,  289 

theory  of  cementing  action . .    176 
Machinery  employed  in  street 

cleaning 415 

Maine,    construction    of    state 

roads 268 

county     highway     commis- 
sioners    264 

how  to  get  state  aid 265 

maintenance    of    state    aid 

highways 271 

payment  for  state  aid  high- 
ways    270 

powers  of  counties 262 

state  aid  fund 260 

state  aid  highways 258 

state  highway  department .  .   256 
Maintenance,  city  pavements. .     26 

country  roads 25,  203 

earth  roads 121 

necessity  for 205 

state  aid  highways 270 

systems  of 208 

wood  pavement 355 

Marble 115 

Maryland,  construction  of  state 

roads 266 

county     highway     commis- 
sioners     262 

how  to  get  state  aid 264 

maintenance    of    state    aid 

highways 270 

payment  for  state  aid  high- 
ways    268 

powers  of  counties 260 

specifications   for   state   aid 

roads 291 

state  aid  fund 258 

state  aid  highways 257 

state  highway  department  .  .  253 
Masonry  bridges 79 


Masonry  bridges,  Portland  ce- 
ment concrete,  specifi- 
cations  

Massachusetts,  county  high- 
way commissioners 

construction  of  state  roads .  . 

highway  commission 

how  to  get  state  aid 

maintenance    of    state    aid 

highways 

payment  for  state  aid  high- 
highways 

powers  of  counties 

specifications   for   state   aid 

roads 

state  aid  fund 

state  aid  highways 

state  highway  department  .  . 
Materials,  broken  stone  roads. . 

concrete  pavements 

employed  for  curbing 

for  different  purposes 

in  road  construction 

in  sidewalks 

new,  application  to  country 

roads  

telford  and  macadam 

Maximum  grade,  determina- 
tion   

most  suitable 

Mechanical    agencies    of    road 

destruction 

Memoir 

Method  of  cutting  planks  from 


drainage 

dust  prevention 218, 

expressing  grade 

employed  in  location 

Michigan,  county  highway 
commissioners 

construction  of  state  roads .  . 

how  to  get  state  aid 

maintenance  of  state  aid 
highways 

payment  for  state  aid  high- 
ways   

powers  of  counties 

state  aid  fund 

state  aid  highways 


274 

263 

266 

24 

264 

270 

269 
261 

272 
259 
257 
254 
166 
390 
444 
34 
91 
425 

207 
161 

46 
47 

95 

43 

339 
65 

225 
18 
41 

263 

2<>7 
265 

271 

270 
262 
260 
258 


540 


INDEX 


Michigan  state  highway  depart- 
ment    256 

Minimum  grade,  establishment  48 

Miscellaneous  roads 450 

Model  bill,  construction  of  state 

roads 265 

county     highway     commis- 
sioners    262 

how  to  get  state  aid 264 

maintenance    of    state    aid 

highways 270 

payment  for  state  aid  high- 
ways   268 

state  aid  funds 258 

state  aid  highways 256 

state  highway  department .  .  253 

Moisture  for  dust  prevention.  .  227 
Morin's    experiments,    general 

results 14 

Mountain  roads 189 

Municipal  growth  in  America . .  405 


X 


Natural  slope  of  embankments     55 
New    Jersey,    construction    of 

state  roads 267 

county     highway     commis- 
sioners    263 

how  to  get  state  aid 264 

maintenance    of    state    aid 

highways 271 

payment  for  state  aid  high- 
ways    269 

powers  of  counties 261 

specifications   for   state   aid 

roads 281 

state  aid  fund 259 

state  aid  highways 257 

state  highway  department.  .    255 
New  York,  construction  of  state 

roads 265 

county     highway     commis- 
sioners     262 

how  to  get  state  aid 264 

maintenance    of    state    aid 

highways :  .   270 

payment  for  state  aid  high- 
ways    268 

powers  of  counties 260 


New  York,    specifications    for 

state  aid  roads 283 

state  aid  funds 258 

state  aid  highways 256 

state  highway  department .  .  253 

O 

Object  of  pavements 28 

roads 10 

Objection  to  steep  grades 18 

Odometer 43 

Ohio,     construction     of    state 

roads 267 

county     highway     commis- 
sioners   263 

how  to  get  state  aid 265 

maintenance    of    state    aid 

highways 271 

payment  for  state  aid  high- 
ways   269 

powers  of  counties 261 

state  aid  fund 259 

state  aid  highways 258 

state  highway  department .  .  255 

Oil  emulsions 228 

Oiling  roads,  rules  for 231 

Oils  for  dust  prevention 229 

Opening  of  pavements 27 

Organic  agencies  of   road   de- 
struction    96 

Organization  in  street  cleaning  419 

Oscillating  crushers 179 

Overcoming  grades,  methods.  .  46 


Park    drives,     materials     em- 
ployed    34 

Patching  country  roads' 216 

Paths  for  parks 428 

Pavements,  asphalt  block 376 

Belgian  block 315 

brick 323 

coal-tar 377 

cobblestone. 313 

comparative  cleanliness 415 

comparative  values 31 

concrete 380 

concrete  cubes 399 

definition..  28 


INDEX 


541 


Pavements,  economics 19 

granite  block 316 

guarantees 487 

Hassam 389 

history .  .       5 

miscellaneous 450 

selection  of 28 

steep  grades 321 

width  of 305 

wood  block 335 

Paving  blocks,  essential  quali- 
ties       96 

bricks,  manufacture 325 

stones Ill 

Payment  for  city  pavements  .  .     22 

state  aid  highways 268 

Pedometer 43 

Pennsylvania,  construction  of 

state  roads 266 

county     highway     commis- 
sioners    263 

how  to  get  state  aid 264 

maintenance    of    state    aid 

highways 271 

payment  for  state  aid  high- 
ways    269 

powers  of  counties 261 

specifications    for    state    aid 

roads 289 

state  aid  fund 259 

state  highway  department .  .   255 

state  aid  highways 257 

Petroleum  for  dust  prevention .  229 
Physical  agencies  causing  road 

destruction 93 

properties  of  rocks 107 

Pipe,   specifications 277 

Plank  roads 455 

Planning  city  streets,  object  of  296 
Plans  for  location  of  city  streets  299 
Planting  trees  on  roadside.  ...  471 

Plate  girder  bridges 79 

Pleasure  drives,  materials  em- 
ployed       34 

Ploughs  for  road  work 139 

Portable      bitulithic       paving 

plants 247 

crushing  plant 181 

Power,  loss  on  inclinations. ...      16 
required  to  move  vehicles ...      11 


PAGE 

Power  of  teams 16 

Powers  and  duties  of  counties, 
model  bill  and  various  state 

laws 260 

Preservation  of  wood 344 

Prevention  of  road  dust 218 

Primary   mineral   constituents 

of  rocks 105 

Profile  of  road  section 67 

Progress  in  wood  paving 335 

Properties   of   an   ideal   pave- 
ment       29 

Protective  works 53 

Q 

Quality,  brick  for  pavements .  .  323 

treated  wood  pavement. . .  .  340 

wood  used  for  paving 343 

Qualities,  concrete  pavements.  385 

road-making  stone 96 

R 

Re-coating  country  roads 213 

Reconnoissance 41 

Reconstruction      of      country 

roads 203 

"  Rectangular  "  plan  of  location 

of  streets 299 

Refuse  removal 421 

Removal  of  household  refuse. .  421 

Repairs,  best  season 215 

country  roads 205 

methods  of 213 

earth  roads 121 

effects  of  neglect 212 

wood  pavement 355 

Report  of  U.  S.  Office  of  Public 

Roads  on  tar  macadam.   241 
Requirements  of  a  good  pave- 
ment      28 

Requisites  to  preservation   of 

surface 205 

Resistance  due  to  gradient.  ...      15 

to  traction 10 

Retaining  walls 87 

Rhode  Island,  construction  of 

state  roads 268 

county     highway     commis- 
sioners. . .  .   264 


542 


INDEX 


PAGE 

Rhode  Island,  how  to  get  state 

aid 265 

maintenance    of    state    aid 

highways. 271 

payment  for  state  aid  high- 
ways.....    270 

powers  of  counties 262 

state  aid  fund. 260 

state  aid  highways 258 

state  highway  department .  .    256 

Right-of-way,  width 50 

Roadbed,  earth  roads 119 

specifications 289,  291 

Road    construction,    materials 

used 91 

on  slopes 59 

Road,  definition 28 

development,  history 1 

dragging 145 

dust,  control  and  prevention  218 

value  and  effects 219 

economics 19 

graders 141 

improvements,  value  of 20 

leveling 144 

making,  early  methods 155 

management 23 

object  of 10 

oils,  handling  of 230 

statistics 499 

Roadmen,  instructions 213 

Roads,  miscellaneous 450 

American  and  European ....       4 

mountainous  districts 189 

Peru. 3 

Roman 3,  311 

Roadside,  protection  of 463 

Roadway,  width 49 

Rock  asphalt  macadam 243 

Rock  slopes,  construction  on .  .     60 

Rocks,  classification  of 101 

road  making Ill 

Rolling  friction 13 

macadam  roads 175 

Roman  roads 3,  311 

8 

Safety  of  pavements 35 

Salt  water  for  dust  prevention .  227 

Sand..                                            .  115 


PAGE 

Sand-clay  roads 127 

improvements  of 204 

Sandstone 113 

sidewalks 425 

Sandy  roads 126 

Sanitation,  aim  of 411 

city  streets 401 

Saturation  of  sand  and  clay  ...    127 

Scarifiers 183 

Scrapers 140 

Scraping  roads 216 

Screening  rock '.  .  .  .    181 

Sea  walls 89 

Season  for  repairs 215 

Second  course,  macadam  roads.   171 

Sedimentary  rocks 103 

Selection  of  materials 92 

pavements  for  different  pur- 
poses      28 

trees  for  roadside 470 

Service,  wood  block  pavement .   341 
Serviceability  of  pavements ...      34 

Setting  curbs 446 

Shape  of  blocks  for  wood  block 

pavement 351 

paving  bricks 327 

Shaping  surface,  specifications .    296 

Shell  roads 459 

Short  span  bridges 75 

Shrinkage  of  earthwork 56 

Side  ditches 66 

drains,  specifications 278 

slope  of  mountain  roads.  .  .  .    196 

Sidewalks 424 

Size,  blocks 297 

wood,  stone 351 

paving  bricks 327 

wheels,  effect  of 14 

Slag  roads 457 

Slide  rock 200 

Slope,  sidewalks 424 

Slopes,  construction  on 59 

Specifications 

construction     of     state     aid 

roads 272 

Portland     cement     concrete 

sidewalks 441 

Portland  cement  pavements  390 

proportioning  concrete 399 

street  trees 469 


INDEX 


543 


PAGE 

Springs,  effect  of 14 

Sprinkler,  specifications 286 

Sprinkling  of  roads 227 

Stability  of  road  service 63 

State  aid,  how  to  get 264 

funds,  model  bill  and  various 

state  laws 258 

highways,  maintenance  of  .  .  270 
model  bill  and  various  states  256 

payment  for 268 

specifications  for  construc- 
tion   272 

la\vs 248 

State     highway      department, 
model   bill  and  various 

states 253 

State  roads,  construction  of ...  265 

Statistics  of  American  roads .  . .  499 

Steam  rollers 178 

Steel  trackways 450 

Stone  block  pavements.  .  .    311,  317 

crushers 79 

crushing  plants 181 

distributing  carts 181 

specifications 288 

Stone  filling,  specifications  ....  279 

Si  one  trackways 7,  450 

Straight  edge 183 

roads,  advantages 39 

length 37 

Straightness  in  country  roads.  39 

Street  cleaning 401 

dirt,  disposal 421 

sources 409 

trees,  specifications 469 

Streets,  area  of 304 

city,  design  of 296 

location  of 2!)!) 

width 303 

Subfoundations,  specifications, 

281,  283 

Subgrade  macadam  roads 169 

Suburban      streets,      materials 

employed 34 

Superstructure  for  bridges  ....  83 

Supervision  of  construction  .  .  .  250 

Surface  drainage 67 

earth  roads 119 

graders 144 

Syenite '. 112 


Systems,  drainage. . 
maintenance .  . 


PAC.E 
.  .  .     65 

.    20S 


Tables,    I.   Standard     tractive 

resistances 11 

II.  Resistances  due  to  gra- 
dient       15 

III.  IV,  and  V.  Comparative 
values  of  various  pave- 
ments   31 

VI.  Amount    of    transverse 

rise  required  for  differ- 
ent pavements (>S 

VII.  General  classification  of 
rocks 102 

VIII.  Primary  mineral  con- 
stituents of  rocks  used 

for  roadmaking 107 

IX.  Physical    properties   of 

rocks  for  roadmaking.  .    107 
X.  Average  costs  of  mac- 
adam  work   in  Massa- 
chusetts     187 

XI.  Average  costs  of  mac- 
adam work  in  New  Jersey  187 
XII.  Averages  of  contract 
prices  for  the  several 
construction  items,  ex- 
clusive of  macadam. — 
Massachusetts  Highway 

Commission 188 

XIH.  Widths  of  roadbed  for 
various  sidehill  slopes, 
with  amount  of  mate- 
rial excavated  per  100 

feet 198 

XIV.  Amount  of  excavation 
in  10-foot  cut  into  solid 

rock 200 

XV.  Acres  required  per  mile 
for  different  widths  of 

roadway 305 

Tables,  use  of,  in  selection    of 

pavements 33 

Tar  macadam 237,  241 

Tarring  roads 235 

Tar  spraying  machines. . .   233,  241 
Tarviating 233,  237 


INDEX 


Tearing  up  pavement 27 

Telfqrd    foundation,    specifica- 
tions    281,  290 

Telford,  Thomas 158 

method  of 160 

defects 163 

Testing  paving  bricks 328 

Tests,  road-making  stones  ....     96 

rocks  by  government 116 

Theory  of  road  dragging 149 

Thickness  of  road  surfaces.  .  .  .    175 

Third  course,  macadam  roads. .   172 
Timber,  use  on  bridges.  ......     79 

Tires,  rubber  and  pneumatic .  .      13 

Toll  roads , 6 

Tongue  scrapers 141 

Tools,  asphalt  pavements 369 

concrete  sidewalk 436 

country  road 137 

Top  dressing  for  wood  pave- 
ment   355 

Topographical  map 43 

Toughness  of  stones 97 

Trackways,  concrete  block. . .  .   452 

steel 450 

stone 450 

Tractive  resistance,  causes  of ..      10 

concrete  pavements 383 

wood  block  pavement 343 

Transverse  balancing 54 

contour 67 

Trap  rock 113 

Tree-planting  association 472 

Trees  for  roadside 468 

Tresaguet's  method 159 

Trimming  macadam  roads.  .  .  .    173 
Trusses,  types  of  for  highway 

bridges 73 

Types  of  bridge  trusses 73 

U 

Unclean  streets,  reason  for  ...    411 


Value  of  improvements 203 

Varieties  of  road-making  rocks  111 

Venice,  Cal.,  center  walks 307 

Virginia,  construction  of  state 

roads 266 


Virginia,  county  highway  com- 
missioners    236 

how  to  get  state  aid 264 

maintenance    of    state    aid 

highways 270 

payment  for  state  aid  high- 
ways   268 

powers  of  counties 261 

state  aid  fund 259 

state  aid  highways 257 

state  highway  department .  .  254 

Vitrification  of  bricks 324 

W 

Washington,  B.C.,  regulations 
governing      width       of 

streets 304 

Washington   (state),  construc- 
tion of  state  roads 267 

county     highway     commis- 
sioners   263 

how  to  get  state  aid 265 

maintenance    of    state    aid 

highways 271 

payment  for  state  aid  high- 
ways   269 

powers  of  counties 261 

state  aid  fund 259 

state  aid  highways 258 

state  highway  department.  .  255 
Water,  effect  on  road  founda- 
tions    93 

carts 185 

Wear  of  roads  by  automobiles .  491 
Wearing  surface,  asphalt  pave- 
ment   366 

Wheel  scrapers 141 

tires,  effect  on  earth  roads ...  122 

Wheels,  effect  of  size 14 

Width,  city  streets 303 

mountain  roads 197 

pavement 305 

roadway 49 

sidewalks 424 

Wind,  effect  on  roads 94 

Wood,  used  in  paving 337 

preserving  methods 344 

sidewalks 426 

Wood  block  pavement 335 

Wooden  bridges 79 


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